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1

TEMPORARY CAPTURE OF PLANETESIMALS BY A PLANET FROM THEIR HELIOCENTRIC ORBITS  

SciTech Connect

When planetesimals encounter a planet, they can be temporarily captured by the planet's gravity and orbit about it for an extended period of time before escaping from the planet's vicinity. Such a process may have played an important role in the origin of irregular satellites or the dynamical evolution of short-period comets. Using three-body orbital integration, we study the temporary capture of planetesimals by a planet from their heliocentric eccentric orbits. We examine the dependence of the orbital characteristics during temporary capture as well as the rate of capture on the pre-capture heliocentric orbital parameters. We find that typical orbital size and direction of revolution around the planet change depending on planetesimals' initial eccentricity and energy. When initial eccentricity is so small that Kepler shear dominates the relative velocity between planetesimals and the planet, temporary capture typically occurs in the retrograde direction in the vicinity of the planet's Hill sphere, while large retrograde capture orbits outside the Hill sphere are predominant for large eccentricities. Long prograde capture occurs in a very narrow range of planetesimal eccentricity and energy. We obtain the rate of temporary capture of planetesimals and find that the rate of long capture increases with increasing eccentricity at low and high eccentricities, but decreases with increasing eccentricity in intermediate values of eccentricity. We also examine the dependence of capture rate on the duration of capture and find an approximate power-law dependence.

Suetsugu, Ryo; Ohtsuki, Keiji [Department of Earth and Planetary Sciences, Kobe University, Kobe 657-8501 (Japan); Tanigawa, Takayuki, E-mail: ryo3088@stu.kobe-u.ac.jp [Center for Planetary Science, Kobe University, Kobe 650-0047 (Japan)

2011-12-15

2

Lessons Learned from Natural Space Debris in Heliocentric Orbit: An Analogue for Hazardous Debris in Earth Orbit  

NASA Astrophysics Data System (ADS)

Interplanetary Field Enhancements (IFEs) were discovered almost 30 years ago in the PVO magnetic-field records. Our current understanding is that IFEs result from interactions between solar wind and clouds of nanometer-scale charged dust released in interplanetary collisions. These charged dust clouds are then accelerated by the solar wind and moving away from the Sun at near solar wind speed and detected by spacecraft in heliocentric orbit. The dynamics of the debris in heliocentric orbit is analogous to that mankind has placed into Earth orbit. There are lessons here that are worth exploring. The IFE formation hypothesis was supported by the discovery of co-orbiting materials associated with asteroid 2201 Oljato: IFE rate peaked when Oljato was close and IFE occurrence clustered in the longitudes near which the orbit of Oljato intersects the orbital plane of Venus. A followed up study with Venus Express observations suggested that the co-orbiting materials dissipated in 30 years. An important aspect of this evolution is that at collisional speeds of 20 km/s, a small body can destroy one 106 times more massive. This destruction of large debris by small debris could also be important in the evolution of the terrestrial debris. At 1AU, based on ACE and Wind observations, IFEs have a significant cluster in the longitude range between 195° and 225°. Thus we use the same IFE technique to identify the ‘parent’ Near-Earth Objects of co-orbiting materials which should be responsible for those IFEs. There are more than 5000 JPL documented NEOs whose ecliptic plane crossings are near to or inside the Earth’s orbit and whose orbital periods are less than five years. By comparing their trajectories, we find that the asteroid 138175 is a good candidate for the ‘parent’ body. This asteroid orbits the Sun in a 5.24° inclined elliptical orbit with a period of 367.96 days. Its descending node is at about 206°, where the IFE occurrence rate peaks. We also find that there is a spread of the IFE rate around the descending node, indicating that the co-orbiting materials have significant dispersion about the asteroid’s orbit. In summary, orbiting debris in orbits intersecting at high speeds can destroy itself quite efficiently, but with a long timescale. In deep space, this process is a step on the path between the asteroidal source population and the creation of solar system dust. This may be true for Earth-orbiting debris as well.

Russell, C. T.; Wei, Hanying; Connors, Martin; Lai, Hairong; Delzanno, Gian Luca

3

Probes to the inferior planets—A new dawn for NEO and IEO detection technology demonstration from heliocentric orbits interior to the earth's?  

NASA Astrophysics Data System (ADS)

Recent years have seen a renewed interest in exploration of the interior of the solar system. A number of missions are currently under way, in planning as well as in space, with the primary goal to expand our knowledge on the planets Mercury and Venus. Chemical propulsion missions to Mercury in particular require an extended cruise phase prior to arrival at their destination, usually involving multiple planetary fly-by manoeuvres and many revolutions in heliocentric orbit. The difficulties in discovering and tracking small objects interior to Earth's orbit, mainly due to unfavourable viewing geometry as well as atmospheric interference, have long been noted by the solar system science and planetary defence communities. Space probes in the interior of the solar system are in a position to observe objects near or interior to Earth's orbit in favourable opposition geometry. They are also usually free from planet-related interference, at least while in cruise, and often can be while in planetary eclipse. Dedicated search and survey missions to look for Near and Inner Earth Objects (NEO, IEO) from the vicinity of Earth or low Earth orbit are being planned. In this article, the ad-hoc available as well as near-term planned in-situ capabilities of the optical instrument payloads of space probes to Venus and Mercury are compiled from publications by the respective instrument teams. The small-object detection capabilities of cameras and spectrographs in opposition geometry are estimated by a common method, using data from comparable instruments to supplement missing information where necessary. The on-board cameras are classified according to their small-object detection potential in a technology demonstration of asteroid detection from a heliocentric orbit substantially interior to Earth's.

Grundmann, Jan Thimo; Mottola, Stefano; Drentschew, Maximilian; Drobczyk, Martin; Kahle, Ralph; Maiwald, Volker; Quantius, Dominik; Zabel, Paul; van Zoest, Tim

2013-09-01

4

The Case for a Geocentric rather than Heliocentric Origin of the Late Stage Heavy Bombardment (LHB) of the Moon and Tidal Evolution of its Orbit  

NASA Astrophysics Data System (ADS)

Melt breccia samples returned from the Apollo mission have dates that suggest that the impacts that formed major basins on the Moon occurred between 3.8 and 4.0 Ga i.e., about 0.6 G years after Lunar formation. Three models have been proposed to explain the LHB. Heliocentric models including (1) The period marked the end of large-scale impacts associated with planetary formation and (2) It corresponded to a spike in impacts associated with major reorientation of the solar system (the ‘Nice model’), when the orbits Jupiter and Saturn became resonant, causing the orbits of Uranus and Neptune to become unstable and grow, scattering cometary and asteroidal fragments into Earth-Moon crossing orbits, and a geocentric model (3) It was due to collision with the last of a series of moonlets formed during Earth accretion which were swept up by tidal regression of a large Moon that had been formed near the Earth by a giant impact. While there is no smoking gun for any of these scenarios we will discuss a possible scenario for (3). Numerical calculations show that tidal regression of a large inner Moon sequentially traps exterior smaller moonlets into 2:1 resonance. Resonant trapping rapidly increases the eccentricity of their orbits causing them to become Moon-crossing. If the orbital radii of the moonlets had a resonance or Bode's law-type distribution, for the last collision to take place at 0.6 Gy, the Moon would have been at ~40 RE when it took place. One of the implications is that the associated LHB impacts would have significantly less relative velocity than those derived from asteroidal or cometary distances associated with (1) or (2). This may explain the low content of vapor condensate in the Lunar breccias. The tidal evolution from ~40 RE at 0.6 Gy requires a lower tidal friction than at present, but this has been evident for many years from tidal rhythmite data.

Davis, P. M.; Stacey, F. D.

2009-12-01

5

Simulations of the Solar Orbiter spacecraft interactions with the Solar wind at different heliocentric distances: effects on SWA-EAS measurements  

NASA Astrophysics Data System (ADS)

This presentation focuses on numerical simulations of the Solar Orbiter spacecraft/plasma interactions performed with the Spacecraft Plasma Interaction System (SPIS) software (http://dev.spis.org/projects/spine/home/spis/). This toolkit aims at modelling spacecraft-plasma interactions, based on an electrostatic 3-D unstructured particle-in-cell plasma model. New powerful SPIS functionalities were recently delivered within the extension of the software: SPIS-Science (ESA contract). This version revolutionizes spacecraft/plasma interactions as users are now able to model and configure plasma instrument such as Langmuir probes or particle detectors taking into account instrument characteristics like geometry, materials, energy ranges and resolution, output frequency, field of view ... In the validation context of SPIS-Science functionalities, a simulation campaign was carried out, including several cases of the ESA Solar Orbiter mission. The results presented here specifically focus on particle measurements through the modelling of the Solar Wind Analyzer - Electron Analyzer System instrument (SWA-EAS). Simulations of the spacecraft in different environments have been performed and extensively analysed. A detailed analysis will be presented concerning 1/ the satellite charging and, in particular, differential potentials on the dielectric surfaces of the Solar panels and the High Gain Antenna, which may severely affect low energy EAS measurements, 2/ the surrounding plasma behaviour : potential barriers for secondary and photoelectrons of about -5 V around the vehicle are indeed observed at the mission perihelion of 0.28 AU from the Sun and 3/ a quantification of biases on EAS measurements due to the combined effects of surface potentials, ion wake, and potential barriers. This work proposes a general framework to prepare the analysis of the future Solar Orbiter measurements.

Guillemant, S.; Genot, V. N.; Matéo Vélez, J.; Sarrailh, P.; Louarn, P.; Maksimovic, M.; Owen, C. J.; Hilgers, A. M.

2013-12-01

6

Ancient Greek Heliocentric Views Hidden from Prevailing Beliefs?  

NASA Astrophysics Data System (ADS)

We put forward the working hypothesis that the heliocentric, rather than the geocentric view, of the Solar System was the essential belief of the early Greek philosophers and astronomers. Although most of them referred to the geocentric view, it is plausible that the prevalent religious beliefs about the sacred character of the Earth as well as the fear of prosecution for impiety (asebeia) prevented them from expressing the heliocentric view, even though they were fully aware of it. Moreover, putting the geocentric view forward, instead, would have facilitated the reception of the surrounding world and the understanding of everyday celestial phenomena, much like the modern presentation of the celestial sphere and the zodiac, where the Earth is at the centre and the Sun makes an apparent orbit on the ecliptic. Such an ingenious stance would have set these early astronomers in harmony with the dominant religious beliefs and, at the same time, would have helped them to 'save the appearances', without sacrificing the essence of their ideas. In Hellenistic and Roman times, the prevailing view was still the geocentric one. The brilliant heliocentric theory advanced by Aristarchos in the early third century B.C. was never established, because it met with hostility in Athens - Aristarchos was accused of impiety and faced the death penalty. The textual evidence suggests that the tight connection which existed between religion and the city-state (polis) in ancient Greece, and which led to a series of impiety trials against philosophers in Athens during the fifth and fourth centuries B.C., would have made any contrary opinion expressed by the astronomers seem almost a high treason against the state.

Liritzis, Ioannis; Coucouzeli, Alexandra

2008-03-01

7

Heliocentric zoning of the asteroid belt by aluminum-26 heating  

NASA Technical Reports Server (NTRS)

Variations in petrology among meteorites attest to a strong heating event early in solar system history, but the heat source has remained unresolved. Aluminum-26 has been considered the most likely high-energy, short-lived radionuclide (half-life 0.72 million years) since the discovery of its decay product - excess Mg-26 - in Allende CAI's. Furthermore, observation of relict Mg-26 in an achondritic clast and in feldspars within ordinary chondrites (3,4) provided strong evidence for live Al-26 in meteorite parent bodies and not just in refractory nebular condensates. The inferred amount of Al-26 is consistent with constraints on the thermal evolution of both ordinary and carbonaceous chondrite parent objects up to a few hundred kilometers in diameter. Meteorites can constrain the early thermal evolution of their parent body locations, provided that a link can be established between asteroid spectrophotometric signature and meteorite class. Asteroid compositions are heliocentrically distributed: objects thought to have experienced high metamorphic or even melting temperatures are located closer to the sun, whereas apparently unaltered or mildly heated asteroids are located farther away. Heliocentric zoning could be the result of Al-26 heating if the initial amount of the radionuclide incorporated into planetesimals was controlled by accretion time, which in turn varies with semimajor axis. Analytic expressions for planetary accretion may be integrated to given the time, tau, required for a planetesimal to grow to a specified radius: tau varies as a(sup n), where n = 1.5 to 3 depending on the assumptions about variations in the surface density of the planetesimal swarm. Numerical simulations of planetesimal accretion at fixed semimajor axis demonstrate that variations in accretion time among small planetesimals can be strongly nonlinear depending on the initial conditions and model assumptions. The general relationship with semimajor axis remains valid because it depends only on the initial orbit properties and distribution of the planesimal swarm. In order to demonstrate the basic dependence of thermal evolution on semimajor axis, we parameterized accretion time across the asteroid belt according to tau varies as a(sup n) and calculated the subsequent thermal history. Objects at a specified semimajor axis were assumed to have the same accretion time, regardless of size. We set the initial Al-26/Al-27 ratio = 6 x 10(exp -5) and treated n and tau(sub 0) at a(sub 0) = 3 AU as adjustable parameters. The thermal model included temperature-dependent properties of ice and rock (CM chondrite analog) and the thermodynamic effects of phase transitions.

Grimm, R. E.; Mcsween, H. Y., Jr.

1993-01-01

8

Proof-of-Concept Trajectory Designs for a Multi-Spacecraft, Low-Thrust Heliocentric Solar Weather Buoy Mission  

NASA Technical Reports Server (NTRS)

A new solar weather mission has been proposed, involving a dozen or more small spacecraft spaced at regular, constant intervals in a mutual heliocentric circular orbit between the orbits of Earth and Venus. These solar weather buoys (SWBs) would carry instrumentation to detect and measure the material in solar flares, solar energetic particle events, and coronal mass ejections as they flowed past the buoys, serving both as science probes and as a radiation early warning system for the Earth and interplanetary travelers to Mars. The baseline concept involves placing a mothercraft carrying the SWBs into a staging orbit at the Sun-Earth L1 libration point. The mothercraft departs the L1 orbit at the proper time to execute a trailing-edge lunar flyby near New Moon, injecting it into a heliocentric orbit with its perihelion interior to Earth s orbit. An alternative approach would involve the use of a Double Lunar Swingby (DLS) orbit, rather than the L1 orbit, for staging prior to this flyby. After injection into heliocentric orbit, the mothercraft releases the SWBs-all equipped with low-thrust pulsed plasma thrusters (PPTs)-whereupon each SWB executes a multi-day low-thrust finite bum around perihelion, lowering aphelion such that each achieves an elliptical phasing orbit of different orbital period from its companions. The resulting differences in angular rates of motion cause the spacecraft to separate. While the lead SWB achieves the mission orbit following an insertion burn at its second perihelion passage, the remaining SWBs must complete several revolutions in their respective phasing orbits to establish them in the mission orbit with the desired longitudinal spacing. The complete configuration for a 14 SWB scenario using a single mothercraft is achieved in about 8 years, and the spacing remains stable for at least a further 6 years. Flight operations can be simplified, and mission risk reduced, by employing two mothercraft instead of one. In this scenario: the second mothercraft stays in a libration-point or DLS staging orbit until the first mothercraft has achieved nearly 180 separation from the Earth. The timing of the second mothercraft's subsequent lunar flyby is planned such that this spacecraft will be located 180 from the first mothercraft upon completion of its heliocentric circularization maneuvers. Both groups of satellites then only have to spread out over 180 to obtain full 360 coverage around the Sun.

Muller, Ronald; Franz, Heather; Roberts, Craig; Folta, Dave

2005-01-01

9

Back to the Future: The Return to Heliocentrism  

E-print Network

to the Sun, p2 = a3 #12;Galileo Galilei (1564-1642) � The first experimental physicist? � Demonstrated stars in the Milky Way #12;#12;#12;#12;Galileo vs. the Pope � The Catholic Church was not anti, heliocentric cosmology � But Galileo insulted Pope Urban VIII in his book Dialogue Concerning the Two Chief

Walter, Frederick M.

10

Heliocentric zoning of the asteroid belt by aluminum-26 heating  

Microsoft Academic Search

The dependence of asteroid spectral class (and inferred composition and thermal history) on heliocentric radius has been held to be the result of heating by a solar energy source, most likely electrical induction, during the formation of the planetary system. Such variations in thermal history can be more simply explained by the presence of different amounts of the radionuclide aluminum-26,

R. E. Grimm; H. Y. Jr. McSween

1993-01-01

11

Spitzer Space Telescope Mission Design  

Microsoft Academic Search

This paper gives a description of the mission design, launch, orbit, and navigation results for the Spitzer space telescope mission. The Spitzer telescope was launched by the Delta I1 Heavy launch vehicle into a heliocentric Earth trailing orbit. This orbit is flown for the fnst time and will be used by several future astronomical missions such as Kepler, SIM, and

Johnny H. Kwok; Mark D. Garcia; Eugene Bonfiglio; Stacia M. Long

12

Heliocentric zoning of the asteroid belt by aluminum-26 heating  

SciTech Connect

The dependence of asteroid spectral class (and inferred composition and thermal history) on heliocentric radius has been held to be the result of heating by a solar energy source, most likely electrical induction, during the formation of the planetary system. Such variations in thermal history can be more simply explained by the presence of different amounts of the radionuclide aluminum-26, whose decay products are observed in meteorites, in planetesimals. These differences occurred naturally as a function of the increasing amount of time required to accrete objects farther from the sun, during which aluminum-26 decayed from its initial concentration in the solar nebula. Both theory and isotopic evidence suggest that increases in accretion time across the asteroid belt are of order several half-lives of aluminum-26, which is sufficient to produce the inferred differences in thermal history. 35 refs., 1 fig.

Grimm, R.E. (Arizona State Univ., Tempe (United States)); McSween, H.Y. Jr. (Univ. of Tennessee, Knoxville (United States))

1993-01-29

13

Application of the heliocentric potential to aircraft dosimetry.  

PubMed

The heliocentric potential is the result of a steady-state solution to the diffusion equation of cosmic rays through the solar wind. The counting rate of any high-latitude, ground-level neutron monitor can be used to determine this potential, which will return cosmic ray spectra in real time. These spectra are routinely used to determine the radiation dose rate to which air crew are exposed during the precise hours of a flight, including the effects of quick decreases and Forbush decreases. Further, it has been used in an effort to calculate the radiation dose rate to air crew during an energetic solar particle event, as the cosmic ray background before the event must be determined. An alternate approach is to use the deceleration potential, which assumes a significant time-dependence of cosmic rays through the heliosphere. However, the theory behind it does not account for the behaviour of ground-level neutron monitors. PMID:16604656

O'Brien, Keran; Felsberger, Ernst; Kindl, Peter

2005-01-01

14

THE DISTRIBUTION OF QUIET-SUN MAGNETIC FIELDS AT DIFFERENT HELIOCENTRIC ANGLES  

SciTech Connect

This paper presents results from the analysis of high signal-to-noise ratio spectropolarimetric data taken at four heliocentric angles in quiet-Sun internetwork regions with the Hinode satellite. First, we find that the total circular and total linear polarization signals vary with heliocentric angle, at least for fields with large polarization signals. We also report changes on the Stokes V amplitude asymmetry histograms with viewing angle for fields weaker than 200 G. Then, we subject the data to a Milne-Eddington inversion and analyze the variation of the field vector probability density functions with heliocentric angle. Weak, highly inclined fields permeate the internetwork at all heliocentric distances. For fields weaker than 200 G, the distributions of field inclinations peak at 90 Degree-Sign and do not vary with viewing angle. The inclination distributions change for fields stronger than 200 G. We argue that the shape of the inclination distribution for weak fields partly results from the presence of coherent, loop-like magnetic features at all heliocentric distances and not from tangled fields within the field of view. We also find that the average magnetic field strength is about 180 G (for 75% of the pixels) and is constant with heliocentric angle. The average vertical and horizontal magnetic field components are 70 and 150 G. The latter (former) is slightly greater (smaller) near the limb. Finally, the ratio between the horizontal and vertical components of the fields ranges from {approx}1 for strong fields to {approx}3.5 for weak fields, suggesting that the magnetic field vector is not isotropically distributed within the field of view.

Orozco Suarez, D.; Katsukawa, Y., E-mail: d.orozco@nao.ac.jp [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan)

2012-02-20

15

From Pythagoreans to Kepler: the dispute between the geocentric and the heliocentric systems  

NASA Astrophysics Data System (ADS)

Some ancient Greek philosophers and thinkers questioned the geocentric system and proposed instead a heliocentric system. The main proponents of this view - which was seen as heretical at the time - are believed to have been the Pythagoreans Philolaos, Heraclides, Hicetas, and Ecphantos, but mainly Aristarchos of Samos, who placed the Sun in the position of the "central fire" of the Pythagoreans. The geocentric system, reworked by Claudius Ptolemaeus (Ptolemy), was the dominant one for centuries, and it was only during the sixteenth century that the Polish monk-astronomer, Copernicus, revisited the ancient Greek heliocentric views and became the new champion of the theory that we all accept today.

Theodossiou, E.; Danezis, E.; Manimanis, V. N.; Kalyva, E.-M.

2002-06-01

16

Development of a Circum-Embryo Debris Disk Model Subject to Collisions from the Heliocentric Swarm  

NASA Astrophysics Data System (ADS)

Collisionally generated debris disks have been extensively studied in the formation of various bodies in our solar system, yet planetary accretion models typically assume the evolving bodies are spherical objects. It is our goal to understand how the existence of debris disks may affect the growth rates of protoplanets in the early solar system. To do this we have constructed a model to calculate the surface mass density profile of a debris disk orbiting an actively accreting body subject to collisions with impactors from a heliocentric protoplanetary disk. Using the accretion history of a protoplanetary embryo, we solve for the collision environment of the body by calculating the rate at which material impacts the surface of the embryo. Including effects of gravitational focusing, we extrapolate this information as a function of distance from the embryo to find the amount of material passing through the region in which our disk exists. The probability a collision will occur between an impactor and the circum-embryo disk depends on the optical depth of the debris disk at the location of the collision. Given some initial surface mass density profile for the circum-embryo disk, our model calculates how mass within the disk is redistributed by these collisions. Collisions between impactors and material within the circum-embryo disk conserve angular momentum, energy, and mass. Additionally, this model is capable of evolving constant and variably viscous disks, calculating mass transfer within the disk due to the increasing mass of the parent body, and tracking the amount of material moving across the inside boundary of the disk. If the disk is chosen to extend to the surface of the parent body, this material accretes onto the body, increasing its mass, which in turn continues to affect the disk. Efforts to continue developing this model will include the effects of collisions between disk particles and satellite accretion beyond the Roche limit in order to more fully understand how circum-embryo debris disks may affect growth rates for protoplanets undergoing oligarchic growth.

Hesselbrock, Andrew; Larson, Jennifer; Minton, David

2014-11-01

17

Interest of old data for the determination of the heliocentric distance of Pluto  

E-print Network

53 Interest of old data for the determination of the heliocentric distance of Pluto L. Beauvalet1, 75014 Paris, France Abstract Pluto was discovered in 1930. It is also the multiple system which has been known for the longest time with the discovery of its first satellite Charon in 1978. Because of Pluto

18

From Phytagoreans to Kepler: the dispute between the geocentric and the heliocentric systems  

Microsoft Academic Search

Some ancient Greek philosophers and thinkers questioned the geocentric system and proposed instead a heliocentric system. The main proponents of this view - which was seen as heretical at the time - are believed to have been the Pythagoreans Philolaos, Heraclides, Hicetas, and Ecphantos, but mainly Aristarchos of Samos, who placed the Sun in the position of the \\

E. Theodossiou; E. Danezis; V. N. Manimanis; E.-M. Kalyva

2002-01-01

19

The trend of production rates with heliocentric distance for comet P/Halley  

NASA Technical Reports Server (NTRS)

Comet P/Halley was observed spectroscopically in the wavelength range 5200-10,400 A during 10 observing runs, roughly a month apart from 1985 August 28 to 1986 June 6. The observations span a heliocentric distance from 0.73 to 2.52 AU. This data set is analyzed to determine the course of the production rate with heliocentric distance for C2, NH2, CN, and the continuum. The effect of changing the Haser scale lengths and their heliocentric distance dependence is examined. The production rate ratios to water change only in a minor way, but the absolute values of the production rates are more severely affected. Fluorescent efficiencies, or g-factors for the CN red system are calculated, and band intensity ratios for NH2 and CN are presented. Using presently available fluorescence efficiencies and Haser scale lengths, mixing ratios for the parents of C2, CN, and NH2 with respect to water are: 0.34 +/- 0.07%, 0.15 +/- 0.04%, and 0.13 +/- 0.05%. It is found that these mixing ratios are essentially constant over the heliocentric distance range of the observations, implying a rather uniform nucleus and uniform outgassing characteristics, although there are indications of smaller scale day-to-day variations. The results provide strong observational confirmation that water evaporation controls the activity of the comet over the distance range studied. Continuum values Af rho are determined, and their ratios to QH2O are found to have a clear dependence with heliocentric distance approximately r(exp -1.0) with a post-perihelion enhancement. No correlation of the production rate ratios with light curve of P/Halley were found, nor was there any correlation of the C2 or CN production with the dust.

Fink, Uwe

1994-01-01

20

On the Provability of Heliocentrism. II. Leon Foucault and the Rotation of the Earth  

NASA Astrophysics Data System (ADS)

This paper deals with the experimental provability of heliocentrism from the scientific Renaissance in the beginning of the 17th century, till the Industrial Revolution of the 1850s. Foucault's famous pendulum demonstration is documented. We underline the importance of high accuracy of observations, the interdependence of hypotheses and theories, the impact of technological breakthroughs, the role of serendipity, the importance of fast and accurate publishing, and the need for precise science communication and teaching.

Sterken, Christiaan

2007-10-01

21

heliocentric observations  

E-print Network

distances, deep CCD observations have been performed on the fields of several comets in 5--19 AU range, i.e. where the subli­ mation of water ice cannot explain the comae that are observed in some comets

Meech, Karen Jean

22

The stellar perturbations of orbital elements of long-period comets  

Microsoft Academic Search

Perturbations in orbital elements of comets with large heliocentric distances that are caused by nearby stars are calculated by the impulse approximation and by accurate numerical integration using Cowell's method. It is shown that the agreement is sufficiently close for elliptic orbits but rather poor for parabolic orbits. The perturbation of inclination is a few tens of degrees while that

S. Yabushita; I. Hasegawa; K. Kobayashi

1982-01-01

23

A Numerical Study of Comet Mcnaught over a Wide Range of Heliocentric Distances  

NASA Astrophysics Data System (ADS)

A numerical study of Comet McNaught over a wide range of heliocentric distances Yinsi Shou, Michael R. Combi, Martin Rubin, Gabor Toth The Comet C/2006 P1 (McNaught) has a small perihelion distance (0.17 AU) and had a very high production rate during its passage close to the Sun in January and February of 2007. During that period, it was monitored by both ground- and space-based observatories, which provided substantial information about the comet. In early February, the Ulysses spacecraft encountered its ion tail and gave clues to the surrounding solar wind conditions and to the cometary environment. Therefore, Comet McNaught is an ideal object to study the cometary structures under extreme conditions and the solar wind-comet interaction over a wide range of heliocentric distances. A numerical study of Comet McNaught combining two models is conducted. First, a single species magnetohydrodynamics (MHD) [Gombosi et al. (1996, JGR 101, 15233)] simulation is performed using a set of ‘observed’ comet parameters as input. Then a chemistry model [Häberli et al. (1997, Icarus 130, 373)] extracts the streamlines from the MHD model and calculates the densities of different species accounting for photo-dissociation, photo-ionization, electron recombination, ion-molecule and charge-exchange reactions. The MHD results are able to give the diamagnetic cavity sizes and shock distances at various heliocentric distances while the chemistry model better resolves the distribution of the major chemical species in the cometary plasma environment. The combination of the two models allows us to obtain detailed information on the chemical composition of a much wider range of atoms and molecules compared to multi-species or multi-fluid MHD models and at much lower computational expense. Some preliminary results are presented and discussed. This work has been partially supported by grant AST-0707283 from the NSF Planetary Astronomy program and NASA Planetary Atmospheres program grant NNX09AB59G.

Shou, Yinsi; Combi, M. R.; Rubin, M.; Toth, G.

2012-10-01

24

Sublimation rates of carbon monoxide and carbon dioxide from comets at large heliocentric distances  

NASA Technical Reports Server (NTRS)

Using a simple model for outgassing from a small flat surface area, the sublimation rates of carbon monoxide and carbon dioxide, two species more volatile than water ice that are known to be present in comets, are calculated for a suddenly activated discrete source on the rotating nucleus. The instantaneous sublimation rate depends upon the comet's heliocentric distance and the Sun's zenith angle at the location of the source. The values are derived for the constants of CO and CO2 in an expression that yields the local rotation-averaged sublimation rate as a function of the comet's spin parameters and the source's cometocentric latitude.

Sekanina, Zdenek

1992-01-01

25

Effect of a drag force due to absorption of solar radiation on solar sail orbital dynamics  

NASA Astrophysics Data System (ADS)

While solar electromagnetic radiation can be used to propel a solar sail, it is shown that the Poynting-Robertson effect related to the absorbed portion of the radiation leads to a drag force in the transversal direction. The Poynting-Robertson effect is considered for escape trajectories, Heliocentric bound orbits and non-Keplerian bound orbits. For escape trajectories, this drag force diminishes the cruising velocity, which has a cumulative effect on the Heliocentric distance. For Heliocentric and non-Keplerian bound orbits, the Poynting-Robertson effect decreases its orbital speed, thereby causing it to slowly spiral towards the Sun. Since the Poynting-Robertson effect is due to the absorbed portion of the electromagnetic radiation, degradation of a solar sail implies that this effect becomes enhanced during a mission.

Kezerashvili, Roman Ya.; Vázquez-Poritz, Justin F.

2013-03-01

26

The Kepler Mission: A wide-field transit search for terrestrial planets  

Microsoft Academic Search

The Kepler Mission is a NASA Discovery mission which will continuously monitor the brightness of at least 100,000 main sequence stars, to detect the transits of terrestrial and larger planets. It is scheduled to be launched in 2007 into an Earth-trailing heliocentric orbit. It is a wide-field photometer with a Schmidt-type telescope and array of 42 CCDs covering the 100

Gibor Basri; William J. Borucki; David Koch

2005-01-01

27

Spitzer Orbit Determination During In-orbit Checkout Phase  

NASA Technical Reports Server (NTRS)

The Spitzer Space Telescope was injected into heliocentric orbit on August 25, 2003 to observe and study astrophysical phenomena in the infrared range of frequencies. The initial 60 days was dedicated to Spitzer's "In-Orbit Checkout (IOC)" efforts. During this time high levels of Helium venting were used to cool down the telescope. Attitude control was done using reaction wheels, which in turn were de-saturated using cold gas Nitrogen thrusting. Dense tracking data (nearly continuous) by the Deep Space network (DSN) were used to perform orbit determination and to assess any possible venting imbalance. Only Doppler data were available for navigation. This paper deals with navigation efforts during the IOC phase. It includes Dust Cover Ejection (DCE) monitoring, orbit determination strategy validation and results and assessment of non-gravitational accelerations acting on Spitzer including that due to possible imbalance in Helium venting.

Menon, Premkumar R.

2004-01-01

28

LISA Orbits  

NASA Astrophysics Data System (ADS)

The LISA formation is composed of 3 spacecraft in an equilateral triangle formation. The baseline formation has a 5million km radius and lies in a heliocentric orbit 20deg away from the Earth. Earth's gravity induces a perturbation on the nominal Keplerian motion of the formation, generating a change in the relative ranges and thus a Doppler that can be very harmful for the scientific goals of the mission. Zero station keeping options are preferred, so alternative passive solutions have to be found. This paper presents results obtained by optimising the formation design, particularly the orientation of the eccentricity vectors. Formation design optimisation proves to be an effective strategy, succeeding in keeping the relative range rate between any two spacecraft below 13m/s. Another possible source of perturbation arises from the self-acceleration induced on the formation by the imperfect mass distribution on each spacecraft. The effect of this perturbing acceleration on the motion of the formation has been studied, and the formation design has been re-optimised assuming several levels of perturbation. This approach has shown the result that such effect can be even beneficial on the formation stability, provided that the acceleration doesn't exceed 1e-8m/s2. The transfer to the optimal stability formation has then been optimised, assuming a launch window throughout the year. Mission ?v to a specific target is quite sensitive to the launch date: trailing formations are most effectively reached if the launch occurs at Earth's apohelion (summer), while the opposite applies to leading formations. A strategy where leading and trailing formations are alternatively targeted according to the launch date has proved to be the most effective in keeping the ?v as low as possible.

Povoleri, Angelo; Kemble, Stephen

2006-11-01

29

Telemetry coding study for the international magnetosphere explorers, mother/daughter and heliocentric missions. Volume 2: Final report  

NASA Technical Reports Server (NTRS)

A convolutional coding theory is given for the IME and the Heliocentric spacecraft. The amount of coding gain needed by the mission is determined. Recommendations are given for an encoder/decoder system to provide the gain along with an evaluation of the impact of the system on the space network in terms of costs and complexity.

Cartier, D. E.

1973-01-01

30

32ND INTERNATIONAL COSMIC RAY CONFERENCE, BEIJING 2011 Heliocentric Distance of CMEs at the Time of Energetic Particle Release: Revisit-  

E-print Network

of Energetic Particle Release: Revisit- ing the Ground Level Enhancement Events of Solar Cycle 23 NAT of the energetic particles during the ground level enhancement (GLE) events of Solar Cycle 23. We find that the GLE particles are released when the CMEs reach an average heliocentric distance of ~3.6 solar radii (Rs

Usoskin, Ilya G.

31

A Synoptic Analysis of the Change from the Geocentric to the Heliocentric Conception of the Solar System.  

ERIC Educational Resources Information Center

The changes which occurred in man's view of the solar system from the time of Ptolemy to that of Galileo are presented. Contained is a brief review of the chain of events which resulted in the acceptance of a heliocentric system. Ptolomy's theory is described and a diagram illustrates the paths of the epicycle of Mars according to his geocentric…

Wilson, Roosevelt L.

32

EVOLUTION OF CORONAL MASS EJECTION MORPHOLOGY WITH INCREASING HELIOCENTRIC DISTANCE. I. GEOMETRICAL ANALYSIS  

SciTech Connect

At launch, coronal mass ejections (CMEs) are often approximated as locally cylindrical objects with circular cross sections. However, CMEs have long been known to propagate almost radially away from the Sun along with the bulk solar wind. This has important consequences for the structure of CMEs; an initially circular cross section will be severely flattened by this radial motion. Yet calculations of total flux and helicity transport by CMEs based on in situ observations still use the assumption of a locally cylindrical object. In this paper, we investigate the morphology of an interplanetary CME based upon geometric arguments. By radially propagating an initial cylindrical object that maintains a constant ratio between its expansion speed and bulk flow, A, we show that the flattening, or 'pancaking', of the two-dimensional cross section effectively ceases; the aspect ratios of these CMEs converge to a fixed value as they propagate further into the heliosphere. Thereafter the CME morphology is scale invariant. We predict aspect ratios of 5 {+-} 1 at terrestrial distances. By correlating a planetary shock with an interplanetary shock linked to a CME, these aspect ratios are estimated using in situ measurements in Paper II. These estimates are made at various heliocentric distances.

Savani, N. P.; Kusano, K. [Solar-Terrestrial Environment Laboratory, Nagoya University, Nagoya 464-8601 (Japan); Owens, M. J. [Space Environment Physic Group, University of Reading, Earley Gate, P.O. Box 243, Reading RG6 6BB (United Kingdom); Rouillard, A. P. [College of Science, George Mason University, Fairfax, VA 22030 (United States); Forsyth, R. J. [Blackett Laboratory, Imperial College London, Prince Consort Road London SW7 2BZ (United Kingdom); Shiota, D. [Computational Astrophysics Laboratory, Advanced Science Institute, RIKEN, 2-1, Hirosawa, Wako, Saitama 351-0198 (Japan); Kataoka, R., E-mail: neel.savani02@imperial.ac.uk [Interactive Research Center of Science, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro, Tokyo 152-8551 (Japan)

2011-04-20

33

EVOLUTION OF CORONAL MASS EJECTION MORPHOLOGY WITH INCREASING HELIOCENTRIC DISTANCE. II. IN SITU OBSERVATIONS  

SciTech Connect

Interplanetary coronal mass ejections (ICMEs) are often observed to travel much faster than the ambient solar wind. If the relative speed between the two exceeds the fast magnetosonic velocity, then a shock wave will form. The Mach number and the shock standoff distance ahead of the ICME leading edge is measured to infer the vertical size of an ICME in a direction that is perpendicular to the solar wind flow. We analyze the shock standoff distance for 45 events varying between 0.5 AU and 5.5 AU in order to infer their physical dimensions. We find that the average ratio of the inferred vertical size to measured radial width, referred to as the aspect ratio, of an ICME is 2.8 {+-} 0.5. We also compare these results to the geometrical predictions from Paper I that forecast an aspect ratio between 3 and 6. The geometrical solution varies with heliocentric distance and appears to provide a theoretical maximum for the aspect ratio of ICMEs. The minimum aspect ratio appears to remain constant at 1 (i.e., a circular cross section) for all distances. These results suggest that possible distortions to the leading edge of ICMEs are frequent. But, these results may also indicate that the constants calculated in the empirical relationship correlating the different shock front need to be modified; or perhaps both distortions and a change in the empirical formulae are required.

Savani, N. P.; Kusano, K. [Solar-Terrestrial Environment Laboratory, Nagoya University, Nagoya (Japan); Owens, M. J. [Space Environment Physic Group, University of Reading, Reading (United Kingdom); Rouillard, A. P. [College of Science, George Mason University, Fairfax, VA (United States); Forsyth, R. J. [Blackett Laboratory, Imperial College London, London (United Kingdom); Shiota, D. [Computational Astrophysics Laboratory, Advanced Science Institute, RIKEN, Wako (Japan); Kataoka, R. [Interactive Research Center of Science, Tokyo Institute of Technology, Tokyo (Japan); Jian, L. [Institute of Geophysics and Planetary Physics, University of California, Los Angeles, CA (United States); Bothmer, V., E-mail: neel.savani02@imperial.ac.uk [Institut fuer Astrophysik, Goettingen University, Goettingen (Germany)

2011-05-10

34

A survey on orbital dynamics and navigation of asteroid missions  

NASA Astrophysics Data System (ADS)

Asteroid exploration is currently one of the most concerned topics among international space agencies. Orbital dynamics and navigation are obviously crucial for asteroid exploration. This paper aims to give a brief review on the dynamics, control and navigation of asteroid reconnaissance orbits, including the heliocentric transfer orbit and near asteroid orbit. The developments in optimization techniques of the transfer segment are discussed in detail. We surveyed global researches in this field and made comments on several important progresses. The final section proposed a prospective of future studies with emphasis on the key techniques of these issues in the asteroid exploration missions.

Baoyin, He-Xi; Li, Jun-Feng

2014-06-01

35

Possible Periodic Orbit Control Maneuvers for an eLISA Mission  

NASA Technical Reports Server (NTRS)

This paper investigates the possible application of periodic orbit control maneuvers for so-called evolved-LISA (eLISA) missions, i.e., missions for which the constellation arm lengths and mean distance from the Earth are substantially reduced. We find that for missions with arm lengths of 106 km and Earth-trailing distance ranging from approx. 12deg to 20deg over the science lifetime, the occasional use of the spacecraft micro-Newton thrusters for constellation configuration maintenance should be able to essentially eliminate constellation distortion caused by Earth-induced tidal forces at a cost to science time of only a few percent. With interior angle variation kept to approx. +/-0:1deg, the required changes in the angles between the laser beam pointing directions for the two arms from any spacecraft could be kept quite small. This would considerably simplify the apparatus necessary for changing the transmitted beam directions.

Bender, Peter L.; Welter, Gary L.

2012-01-01

36

Orbit Determination and Navigation of the Solar Terrestrial Relations Observatory (STEREO)  

NASA Technical Reports Server (NTRS)

This paper provides an overview of the required upgrades necessary for navigation of NASA's twin heliocentric science missions, Solar TErestrial RElations Observatory (STEREO) Ahead and Behind. The orbit determination of the STEREO spacecraft was provided by the NASA Goddard Space Flight Center's (GSFC) Flight Dynamics Facility (FDF) in support of the mission operations activities performed by the Johns Hopkins University Applied Physics Laboratory (APL). The changes to FDF's orbit determination software included modeling upgrades as well as modifications required to process the Deep Space Network X-band tracking data used for STEREO. Orbit results as well as comparisons to independently computed solutions are also included. The successful orbit determination support aided in maneuvering the STEREO spacecraft, launched on October 26, 2006 (00:52 Z), to target the lunar gravity assists required to place the spacecraft into their final heliocentric drift-away orbits where they are providing stereo imaging of the Sun.

Mesarch, Michael A.; Robertson, Mika; Ottenstein, Neil; Nicholson, Ann; Nicholson, Mark; Ward, Douglas T.; Cosgrove, Jennifer; German, Darla; Hendry, Stephen; Shaw, James

2007-01-01

37

Solar wind structure between 20 solar radii and the orbit of Mars  

Microsoft Academic Search

The procedure for mapping solar wind fluctuations observed at earth (1 ; AU) to other heliocentric distances under the assumption that they are corotating ; structures has been applied to Explorer 35 solar wind data to obtain solar wind ; structure between 20 Rs and the orbit of Mars. Mappings were obtained for each ; of nine lunations. Two cases

Roy R. Lewis; G. L. Siscoe

1973-01-01

38

Photochemistry of atomic oxygen green and red-doublet emissions in comets at larger heliocentric distances  

NASA Astrophysics Data System (ADS)

Context. In comets, the atomic oxygen green (5577 Å) to red-doublet (6300, 6364 Å) emission intensity ratio (G/R ratio) of 0.1 has been used to confirm H2O as the parent species producing forbidden oxygen emission lines. The larger (>0.1) value of G/R ratio observed in a few comets is ascribed to the presence of higher CO2 and CO relative abundances in the cometary coma. Aims: We aim to study the effect of CO2 and CO relative abundances on the observed G/R ratio in comets observed at large (>2 au) heliocentric distances by accounting for important production and loss processes of O(1S) and O(1D) atoms in the cometary coma. Methods: Recently we have developed a coupled chemistry-emission model to study photochemistry of O(1S) and O(1D) atoms and the production of green and red-doublet emissions in comets Hyakutake and Hale-Bopp. In the present work we applied the model to six comets where green and red-doublet emissions are observed when they are beyond 2 au from the Sun. Results: The collisional quenching of O(1S) and O(1D) can alter the G/R ratio more significantly than that due to change in the relative abundances of CO2 and CO. In a water-dominated cometary coma and with significant (>10%) CO2 relative abundance, photodissociation of H2O mainly governs the red-doublet emission, whereas CO2 controls the green line emission. If a comet has equal composition of CO2 and H2O, then ~50% of red-doublet emission intensity is controlled by the photodissociation of CO2. The role of CO photodissociation is insignificant in producing both green and red-doublet emission lines and consequently in determining the G/R ratio. Involvement of multiple production sources in the O(1S) formation may be the reason for the observed higher green line width than that of red lines. The G/R ratio values and green and red-doublet line widths calculated by the model are consistent with the observation. Conclusions: Our model calculations suggest that in low gas production rate comets the G/R ratio greater than 0.1 can be used to constrain the upper limit of CO2 relative abundance provided the slit-projected area on the coma is larger than the collisional zone. If a comet has equal abundances of CO2 and H2O, then the red-doublet emission is significantly (~50%) controlled by CO2 photodissociation and thus the G/R ratio is not suitable for estimating CO2 relative abundance.

Raghuram, Susarla; Bhardwaj, Anil

2014-06-01

39

Gravity and Orbits: Orbits  

NSDL National Science Digital Library

This Science Object is the third of three Science Objects in the Gravity and Orbits SciPack. It provides an understanding of how gravitational forces influence the motion of an object in orbit. When a force acts toward a single center, an object's forward motion and its motion toward that center can combine to create a curved path around the center. Gravity governs the motion of all objects in the solar system. The Sun's gravitational pull holds the Earth and other planets in their orbits, just as the planets' gravitational pull keeps their moons in orbit around them. Learning Outcomes:� Describe the conditions that would lead an object into orbital motion in terms of the effects of gravitational force.� Explain how an object orbits a planet in terms of trajectories and free fall.� Identify gravity as the force that keeps the planets in their orbits around the Sun and the moons in their orbits around the planets.

National Science Teachers Association (NSTA)

2006-11-01

40

Organic ices in the coma of comet C/2012 S1 (ISON) at heliocentric distances greater than 4 AU?  

NASA Astrophysics Data System (ADS)

Comet C/2012 S1 (ISON) was monitored during its approach to the inner solar system, when the comet passed from a heliocentric distance of 6.0 to 4.3 AU. As many other Oort cloud comets at their first approach to the Sun, also comet ISON exhibited a systematic over population of grains in the inner part of the coma, as revealed by the ?Af function (Tozzi et al., 2007, A&A 476, 979). So far this effect has been interpreted as due either to a short timescale variation of activity (outbursts), or long timescale variation of activity associated with very low escape velocity of the grains or with sublimating grains. In the presentation we will show that the most likely explanation of the phenomena is the sublimation of icy CO2 grains. We will discuss also the implication of CO2 production rates by this distributed source on the whole gas production rates of the comet at so large heliocentric distances.

Tozzi, Gian-Paolo; Faggi, Sara; Brucato, John R.; Bruni, Ivan; Licandro, Javier; Mazzotta Epifani, Elena; Meech, Karen; Mottola, Stefano; Watanabe, Makoto

2014-11-01

41

Method of determining the orbits of the small bodies in the solar system based on an exhaustive search of orbital planes  

NASA Astrophysics Data System (ADS)

A universal method of determining the orbits of newly discovered small bodies in the Solar System using their positional observations has been developed. The proposed method suggests determining geocentric distances of a small body by means of an exhaustive search for heliocentric orbital planes and subsequent determination of the distance between the observer and the points at which the chosen plane intersects with the vectors pointing to the object. Further, the remaining orbital elements are determined using the classical Gauss method after eliminating those heliocentric distances that have a fortiori low probabilities. The obtained sets of elements are used to determine the rms between the observed and calculated positions. The sets of elements with the least rms are considered to be most probable for newly discovered small bodies. Afterwards, these elements are improved using the differential method.

Bondarenko, Yu. S.; Vavilov, D. E.; Medvedev, Yu. D.

2014-05-01

42

Kepler Stars with Multiple Transiting Planet Candidates  

NASA Technical Reports Server (NTRS)

NASA's Kepler spacecraft was launched into an Earth-trailing heliocentric orbit in March of 2009. Kepler is designed to conduct a statistical census of planetary system properties using transit photometry. Among the most exciting early results from Kepler are target stars found to have photometric signatures that suggest the presence of more than one transiting planet. Individual transiting planets provide information on the size and orbital period distributions of exoplanets. Multiple transiting planets provide additional information on the spacing and flatness distributions of planetary systems. Results to d ate and plans for future analysis will be presented.

Lissauer, Jack J.

2012-01-01

43

Program manual for HILTOP, a heliocentric interplanetary low thrust trajectory optimization program. Part 1: User's guide  

NASA Technical Reports Server (NTRS)

A performance-analysis computer program, that was developed explicitly to generate optimum electric propulsion trajectory data for missions of interest in the exploration of the solar system is presented. The program was primarily designed to evaluate the performance capabilities of electric propulsion systems, and in the simulation of a wide variety of interplanetary missions. A numerical integration of the two-body, three-dimensional equations of motion and the Euler-Lagrange equations was used in the program. Transversality conditions which permit the rapid generation of converged maximum-payload trajectory data, and the optimization of numerous other performance indices for which no transversality conditions exist are included. The ability to simulate constrained optimum solutions, including trajectories having specified propulsion time and constant thrust cone angle, is also in the program. The program was designed to handle multiple-target missions with various types of encounters, such as rendezvous, stopover, orbital capture, and flyby. Performance requirements for a variety of launch vehicles can be determined.

Mann, F. I.; Horsewood, J. L.

1974-01-01

44

Orbital Resonance and Solar Cycles  

E-print Network

We present an analysis of planetary moves, encoded in DE406 ephemerides. We show resonance cycles between most planets in Solar System, of differing quality. The most precise resonance - between Earth and Venus, which not only stabilizes orbits of both planets, locks planet Venus rotation in tidal locking, but also affects the Sun: This resonance group (E+V) also influences Sunspot cycles - the position of syzygy between Earth and Venus, when the barycenter of the resonance group most closely approaches the Sun and stops for some time, relative to Jupiter planet, well matches the Sunspot cycle of 11 years, not only for the last 400 years of measured Sunspot cycles, but also in 1000 years of historical record of "severe winters". We show, how cycles in angular momentum of Earth and Venus planets match with the Sunspot cycle and how the main cycle in angular momentum of the whole Solar system (854-year cycle of Jupiter/Saturn) matches with climatologic data, assumed to show connection with Solar output power and insolation. We show the possible connections between E+V events and Solar global p-Mode frequency changes. We futher show angular momentum tables and charts for individual planets, as encoded in DE405 and DE406 ephemerides. We show, that inner planets orbit on heliocentric trajectories whereas outer planets orbit on barycentric trajectories.

P. A. Semi

2009-03-29

45

Nuclear-electric reusable orbital transfer vehicle  

NASA Technical Reports Server (NTRS)

To help determine the systems requirements for a 300-kWe space nuclear reactor power system, a mission and spacecraft have been examined that utilize electric propulsion supported by the nuclear reactor's power for multiple transfers of cargo between low earth orbit (LEO) and geosynchronous earth orbit (GEO). A propulsion system employing ion thrusters and xenon propellant was selected. Propellant and thrusters are replaced after each sortie to GEO. The mass of the orbital transfer vehicle (OTV), empty and dry, is 11,000 kg; nominal propellant load is 5000 kg. The OTV operates between a circular orbit at 925-km altitude, 28.5-deg inclination, and GEO. Cargo is brought to the OTV by Shuttle and an orbital maneuvering vehicle (OMV); the OTV then takes it to GEO. The OTV can also bring cargo back from GEO for transfer by OMV to the Shuttle. OTV propellant is resupplied, and the ion thrusters are replaced, by the OMV before each sortie to GEO. At the end of mission life, the OTV's electric propulsion is used to place it in a heliocentric orbit so that the reactor will not return to earth. The nominal cargo capability to GEO is 6000 kg, with a transit time of 120 days; 1350 kg can be transferred in 90 days, and 14,300 kg in 240 days. These capabilities can be considerably increased by using separate Shuttle launches to bring up propellant and cargo or by changing to mercury propellant.

Jaffe, Leonard D.

1988-01-01

46

Characteristics of large Forbush-type decreases in the cosmic radiation. II - Observations at different heliocentric radial distances  

NASA Technical Reports Server (NTRS)

Cosmic ray data from IMP 8, Voyager 1 and 2, Pioneer 10 are used to investigate the heliocentric radial dependence of the characteristics of about 20 Forbush-type transient decreases which occurred from 1978 to 1984. These characteristics include the recovery time, the amplitude, and the time to decrease to minimum. It is found that the average recovery time is about 5 times longer at R = 30 AU than at 1 AU. The magnitudes of the transient decreases are observed to decrease about 1.5 percent/AU on average so that the magnitude of the decrease is half as great at R about 30 AU as at 1 AU. The time for the cosmic ray intensity to decrease to the minimum in the transient decrease is found to be greater at larger distances and is about 5 times longer at R = 30 AU than at 1 AU. The behavior of these effects as a function of radius is obviously related to the evolution of the disturbances causing the transient decreases as they propagate outward. A model of the Forbush-type decrease is proposed to explain the observed radial dependence of the recovery time and time to minimum of the decrease. The implications of these results for understanding the relationship between Forbush-type decreases and the 11-year variation are discussed.

Webber, W. R.; Lockwood, J. A.; Jokipii, J. R.

1986-01-01

47

The Side-Looking Coronagraph (SILC) for the Solar Orbiter mission: optical performances  

NASA Astrophysics Data System (ADS)

The SIde-Looking Coronagraph (SILC) is one of the solar remote-sensing instruments proposed for the payload of the Solar Orbiter mission (European Space Agency, ESA). The specificities of the Solar Orbiter mission are very restrictive for a coronagraph: large range of heliocentric distance from 0.21 to 0.6 AU, offset pointing capability of the spacecraft, severe thermal environment of limited mass and volume available. To cope with them, we propose an externally occulted coronagraph entirely protected from direct sunlight by remaining in the shadow of the spacecraft and looking sideways. The optical design follows the general principles of an externally-occulted coronagraph adapted to the side-looking concept. The performances and the expected stray light level will be presented here together with their evolution as function of the heliocentric distance.

Vivès, Sébastien; Lamy, Philippe

2004-06-01

48

Kepler's Orbit  

NASA Video Gallery

Kepler does not orbit the Earth, rather it orbits the Sun in concert with the Earth, slowly drifting away from Earth. Every 61 Earth years, Kepler and Earth will pass by each other. Throughout the ...

49

A STUDY OF THE HELIOCENTRIC DEPENDENCE OF SHOCK STANDOFF DISTANCE AND GEOMETRY USING 2.5D MAGNETOHYDRODYNAMIC SIMULATIONS OF CORONAL MASS EJECTION DRIVEN SHOCKS  

SciTech Connect

We perform four numerical magnetohydrodynamic simulations in 2.5 dimensions (2.5D) of fast coronal mass ejections (CMEs) and their associated shock fronts between 10 Rs and 300 Rs. We investigate the relative change in the shock standoff distance, {Delta}, as a fraction of the CME radial half-width, D {sub OB} (i.e., {Delta}/D {sub OB}). Previous hydrodynamic studies have related the shock standoff distance for Earth's magnetosphere to the density compression ratio (DR; {rho} {sub u}/{rho} {sub d}) measured across the bow shock. The DR coefficient, k {sub dr}, which is the proportionality constant between the relative standoff distance ({Delta}/D {sub OB}) and the compression ratio, was semi-empirically estimated as 1.1. For CMEs, we show that this value varies linearly as a function of heliocentric distance and changes significantly for different radii of curvature of the CME's leading edge. We find that a value of 0.8 {+-} 0.1 is more appropriate for small heliocentric distances (<30 Rs) which corresponds to the spherical geometry of a magnetosphere presented by Seiff. As the CME propagates its cross section becomes more oblate and the k {sub dr} value increases linearly with heliocentric distance, such that k {sub dr} = 1.1 is most appropriate at a heliocentric distance of about 80 Rs. For terrestrial distances (215 Rs) we estimate k {sub dr} = 1.8 {+-} 0.3, which also indicates that the CME cross-sectional structure is generally more oblate than that of Earth's magnetosphere. These alterations to the proportionality coefficients may serve to improve investigations into the estimates of the magnetic field in the corona upstream of a CME as well as the aspect ratio of CMEs as measured in situ.

Savani, N. P. [University Corporation for Atmospheric Research (UCAR), Boulder, CO 80307 (United States); Shiota, D. [Computational Astrophysics Laboratory, Advanced Science Institute, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Kusano, K. [Solar-Terrestrial Environment Laboratory, Nagoya University, Nagoya 464-8601 (Japan); Vourlidas, A. [Space Science Division, Naval Research Laboratory, Washington, DC 20375-5352 (United States); Lugaz, N., E-mail: neel.savani02@imperial.ac.uk [Experimental Space Plasma Group, University of New Hampshire, Durham, NH 03824 (United States)

2012-11-10

50

Orbit Program  

NSDL National Science Digital Library

The Orbit program displays the dynamics of multiple massive objects interacting gravitationally. The default scenario shows the figure-eight orbit of three particles first discovered by Montgomery. Additional particles and their initial positions and velocities can be specified using the Display | Switch GUI menu item. Orbit is an Open Source Physics program written for the teaching of classical orbits. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the mech_orbit.jar file will run the program if Java is installed. Other classical mechanics programs are also available. They can be found by searching ComPADRE for Open Source Physics, OSP, or mechanics.

Christian, Wolfgang

2008-05-20

51

The stellar perturbations of orbital elements of long-period comets  

NASA Astrophysics Data System (ADS)

Perturbations in orbital elements of comets with large heliocentric distances that are caused by nearby stars are calculated by the impulse approximation and by accurate numerical integration using Cowell's method. It is shown that the agreement is sufficiently close for elliptic orbits but rather poor for parabolic orbits. The perturbation of inclination is a few tens of degrees while that of perihelion distance is from a few to a few tens of Au depending on mutual configurations. For random encounters, statistical parameters which specify the distributions of orbital elements are calculated by the Monte Carlo method. For direct orbits, the perturbations are such as to increase the inclination, while if the initial orbit is retrograde, the tendency is for the inclination to decrease. An almost complete randomization of inclinations will take place within a few million years.

Yabushita, S.; Hasegawa, I.; Kobayashi, K.

1982-08-01

52

Low cost transfer into useful sun-synchronous orbits at Mars  

NASA Technical Reports Server (NTRS)

Mars oblateness has been found to provide sun-synchronous orbits, including orbits with stationary apsides, similar to those used at earth. A low mass and low data rate complement of scientific instruments placed in such orbits can provide exciting planetary investigations such as the Mars Orbiter Water Mission described herein. Use of a modest Shuttle kickstage (PAM-A) and existing spacecraft hardware makes this mission low-cost. A preliminary mission and spacecraft design is described. The major emphasis of the paper is on the mechanics of heliocentric transfer for the 1986 and 1988 launch opportunities, Martian sun-synchronous orbit geometries, injectable mass capabilities, and methods of achieving these scientifically useful orbits.

Glickman, R. E.; Stuart, J. R.

1981-01-01

53

Spitzer Space Telescope mission design  

NASA Astrophysics Data System (ADS)

This paper gives a description of the mission design, launch, orbit, and navigation results for the Spitzer space telescope mission. The Spitzer telescope was launched by the Delta II Heavy launch vehicle into a heliocentric Earth trailing orbit. This orbit is flown for the first time and will be used by several future astronomical missions such as Kepler, SIM, and LISA. This paper describes the launch strategy for a winter versus a summer launch and how it affects communications. It also describes how the solar orbit affects the design and operations of the Observatory. It describes the actual launch timeline, launch vehicle flight performance, and the long term behavior of the as flown orbit. It also provides the orbit knowledge from in-flight navigation data.

Kwok, Johnny H.; Garcia, Mark D.; Bonfiglio, Eugene; Long, Stacia M.

2004-10-01

54

Pupils Produce their Own Narratives Inspired by the History of Science: Animation Movies Concerning the Geocentric-Heliocentric Debate  

NASA Astrophysics Data System (ADS)

In this paper, we present the design and application of a teaching scenario appropriate for 12-years-old pupils in the primary school aiming to a better understanding of scientific concepts and scientific methods, linking the development of individual thinking with the development of scientific ideas and facilitating a better understanding of the nature of science. The design of the instructional material supporting this scenario has been based on the study of the history of astronomy and especially on: (a) The various theories concerning the movement of Earth, our solar system and the universe. (b) Key-stories highlighting the evolutionary character of scientific knowledge as well as the cultural interrelations of science and society. The design of the teaching scenario has focused on the participation of pupils in gradually evolving discourses and practices encouraging an appreciation of aspects of the nature of science (e.g. the role of observation and hypothesis, the use of evidence, the creation and modification of models). In this case, pupils are asked to produce their own narratives: animation movies concerning the geocentric-heliocentric debate inspired by the history of science, as the animation technique presents strong expressional potential and currently has many applications in the field of educational multimedia. The research design of this current case study has been based on the SHINE research model, while data coming from pupils' animation movies, questionnaires, interviews, worksheets, story-boards and drawings have been studied and analyzed using the GNOSIS research model. Elaborated data coming from our analysis approach reveal the appearance, transformation and evolution of aspects of nature of science appreciated by pupils and presented in their movies. Data analysis shows that during the application pupils gradually consider more and more the existence of multiple answers in scientific questions, appreciate the effect of culture on the way science functions and the way scientists work as well as the effect of new scientific interpretations that replace the old ones in the light of new evidence. The development of pupils' animation movies carrying aspects of the history of astronomy with a strong focus on the understanding of the nature of science creates a dynamic educational environment that facilitates pupils' introduction to a demanding teaching content (e.g. planet, model, retrograde motion) placing it in context (key-stories from the history of science) and at the same time offers to pupils the opportunity to engage their personal habits, interests and hobbies in the development of their science movies.

Piliouras, Panagiotis; Siakas, Spyros; Seroglou, Fanny

2011-07-01

55

Visible, externally occulted coronagraph for Solar Orbiter  

NASA Astrophysics Data System (ADS)

The SIde-Looking Coronagraph (SILC) is one of the solar remote-sensing instruments proposed for the payload of the Solar Orbiter mission. The Solar Orbiter is a mission selected in September 2000 by the European Space Agency (ESA) for the definition study phase. The Solar Orbiter will describe elliptic orbits with a large range of heliocentric distance, from 0.21 to 0.6 AU (astronomical units), that is a factor 3 for the geometric conditions and will reach heliographic latitudes as high as 38 degrees. Furthermore, the spacecraft will have offset pointing capability so as to target any point of the solar disk. These constraints (in addition to the severe thermal environment) lead us to propose an externally occulted coronagraph entirely protected from direct sunlight by remaining in the shadow of the spacecraft and looking sideways. The optical design follows the general principles of an externally-occulted coronagraph adapted to the side-looking concept. Although SILC loses the full spatial coverage of the corona, it can observe the inner part of the corona (down to 1.5R) during the whole mission and compensate the off-pointing of the spacecraft in the two directions. The performances, resulting from ray-tracing calculations, are presented here together with the expected stray light level.

Vives, Sebastien; Lamy, Philippe L.; Korendyke, Clarence

2004-02-01

56

Physical and orbital properties of the Trojan asteroids  

E-print Network

All the Trojan asteroids orbit about the Sun at roughly the same heliocentric distance as Jupiter. Differences in the observed visible reflection spectra range from neutral to red, with no ultra-red objects found so far. Given that the Trojan asteroids are collisionally evolved, a certain degree of variability is expected. Additionally, cosmic radiation and sublimation are important factors in modifying icy surfaces even at those large heliocentric distances. We search for correlations between physical and dynamical properties, we explore relationships between the following four quantities; the normalised visible reflectivity indexes ($S'$), the absolute magnitudes, the observed albedos and the orbital stability of the Trojans. We present here visible spectroscopic spectra of 25 Trojans. This new data increase by a factor of about 5 the size of the sample of visible spectra of Jupiter Trojans on unstable orbits. The observations were carried out at the ESO-NTT telescope (3.5m) at La Silla, Chile, the ING-WHT (4.2m) and NOT (2.5m) at Roque de los Muchachos observatory, La Palma, Spain. We have found a correlation between the size distribution and the orbital stability. The absolute-magnitude distribution of the Trojans in stable orbits is found to be bimodal, while the one of the unstable orbits is unimodal, with a slope similar to that of the small stable Trojans. This supports the hypothesis that the unstable objects are mainly byproducts of physical collisions. The values of $S'$ of both the stable and the unstable Trojans are uniformly distributed over a wide range, from $0 %/1000\\AA $ to about $15 %/1000\\AA$. The values for the stable Trojans tend to be slightly redder than the unstable ones, but no significant statistical difference is found.

M. D. Melita; J. Licandro; Jones; D. C.; I. P. Williams

2008-01-16

57

Atomic Orbitals  

NSDL National Science Digital Library

The Atomic Orbitals Web site "was established as part of an (ongoing) project at Purdue University to develop 'visualization modules' for general chemistry students." Using the Chime plug-in, which allows unique and stunning visualizations, visitors can learn what an atomic orbital is; what the 1s, 2s, 3s, 2p, 3p, and 3d orbitals are; what hybrid orbitals are; and more. The combination of easy-to-read descriptions and educational graphics make the site a great learning resource for high school and even college level chemistry students.

1969-12-31

58

Heliocentric Distance of Coronal Mass Ejections at the Time of Energetic Particle Release: Revisiting the Ground Level Enhancement Events of Solar Cycle 23  

NASA Technical Reports Server (NTRS)

Using the kinematics of coronal mass ejections (CMEs), onset time of soft X-ray flares, and the finite size of the pre-eruption CME structure, we derive the heliocentric distane at which the energetic particles during the ground level enhancement (GLE) events of Solar Cycle 23. We find that the GLE particles are released when the CMEs reach an average heliocentric distance of approx.3.25 solar radii (Rs). From this we infer that the shocks accelerating the particles are located at similar heights. Type II radio burst observations indicate that the CMEs are at much lower distances (average approx.1.4 Rs) when the CME-driven shock first forms. The shock seems to travel approx.1.8 Rs over a period of approox.30 min on the average before releasing the GLE particles. In deriving these results, we made three assumptions that have observational support: (i) the CME lift off occurs from an initial distance of about 1.25 Rs; (ii) the flare onset and CME onset are one and the same because these are two different manifestations of the same eruption; and (iii) the CME has positive acceleration from the onset to the first appearance in the coronagraphic field of view (2.5 to 6 Rs). Observations of coronal cavities in eclipse pictures and in coronagraphic images justify the assumption (i). The close relationship between the flare reconnection magnetic flux and the azimuthal flux of interplanetary magnetic clouds justify assumption (ii) consistent with the standard model (CSHKP) of solar eruption. Coronagraphic observations made close to the solar surface indicate a large positive acceleration of CMEs to a heliocentric distance of approx.3 Rs before they start slowing down due to the drag force. The inferred acceleration (approx.1.5 km/s/s) is consistent with reported values in the literature.

Gopalswamy, Natchimuthuk

2011-01-01

59

Data catalog series for space science and applications flight missions. Volume 1A: Descriptions of planetary and heliocentric spacecraft and investigations, second edition  

NASA Technical Reports Server (NTRS)

The main purpose of the data catalog series is to provide descriptive references to data generated by space science flight missions. The data sets described include all of the actual holdings of the Space Science Data Center (NSSDC), all data sets for which direct contact information is available, and some data collections held and serviced by foreign investigators, NASA and other U.S. government agencies. This volume contains narrative descriptions of planetary and heliocentric spacecraft and associated experiments. The following spacecraft series are included: Mariner, Pioneer, Pioneer Venus, Venera, Viking, Voyager, and Helios. Separate indexes to the planetary and interplanetary missions are also included.

Cameron, Winifred Sawtell (editor); Vostreys, Robert W. (editor)

1988-01-01

60

Data catalog series for space science and applications flight missions. Volume 1B: Descriptions of data sets from planetary and heliocentric spacecraft and investigations  

NASA Technical Reports Server (NTRS)

The main purpose of the data catalog series is to provide descriptive references to data generated by space science flight missions. The data sets described include all of the actual holdings of the Space Science Data Center (NSSDC), all data sets for which direct contact information is available, and some data collections held and serviced by foreign investigators, NASA and other U.S. government agencies. This volume contains narrative descriptions of planetary and heliocentric spacecraft and associated experiments. The following spacecraft series are included: Mariner, Pioneer, Pioneer Venus, Venera, Viking, Voyager, and Helios. Separate indexes to the planetary and interplanetary missions are also provided.

Horowitz, Richard (compiler); Jackson, John E. (compiler); Cameron, Winifred S. (compiler)

1987-01-01

61

Orbital imaging.  

PubMed

Appropriate axial or coronal computed x-ray tomography is the most inexpensive method to reliably supply detail in orbital disease. Magnetic resonance imaging can provide additional information and may be characteristic in some conditions. Magnetic resonance imaging is imperative for detailed imaging of disease at the orbital apex, optic canal, or chiasm. Color-coded Doppler ultrasonography allows examination of physiological blood flow within orbital vasculature and recent reports have reported the changes of flow in various orbital diseases. Limited results with computed tomographic or video-radiographic investigation of lacrimal outflow obstruction have been presented in several articles, although it remains doubtful whether these techniques are superior to the cheaper, more readily available, conventional macrodacryocystography. Endoscopy of the lacrimal drainage system is proving to be an interesting research tool, but is of uncertain applicability in the treatment of disease. PMID:10146487

Rose, G E

1993-11-01

62

Öpik-type collision probability for high-inclination orbits: Targets on eccentric orbits  

NASA Astrophysics Data System (ADS)

Traditional evaluation of collision probability between two bodies on bound heliocentric or planetocentric orbits include assumptions that are often only an approximation of their real motion. In particular, these approaches require (i) the orbital eccentricity and inclination of both target and projectile long-term constant, and (ii) their longitude of ascending node and argument of pericenter precessing uniformly in time. Both conditions (i) and (ii) are satisfied for orbits with very small eccentricities and inclinations only. When either of these two elements is large, a tidal perturbation by planets, or the Sun in a planetocentric configuration, makes these elements oscillate in a correlation with the non-linear evolution of the secular angles. Vokrouhlický et al. (Vokrouhlický, D., Pokorný, P., Nesvorný, D. [2012]. Icarus 219, 150-160) developed an approach which allows the orbit of the projectile undergo such a general secular evolution. An assumption of the circular orbit of the target, however, was a significant drawback of their method. Here, we extend Vokrouhlický et al.’s work to allow a general eccentric and precessing orbit of the target (assuming though fixed orbital plane in space). We test predictions of our new approach, as well as previous theories, against a direct numerical integration and estimate their validity. A particular run is performed for E-belt projectiles impacting terrestrial planets. We conclude a surprisingly good correspondence of the directly obtained impact record from the numerical simulation and the estimate from our theory. Based on these results, we infer that the crater density from E-belt projectiles on Mercury should be roughly comparable (or only slightly larger) to that on our Moon.

Pokorný, Petr; Vokrouhlický, David

2013-09-01

63

Orbit Determination Accuracy for Comets on Earth-Impacting Trajectories  

NASA Technical Reports Server (NTRS)

The results presented show the level of orbit determination accuracy obtainable for long-period comets discovered approximately one year before collision with Earth. Preliminary orbits are determined from simulated observations using Gauss' method. Additional measurements are incorporated to improve the solution through the use of a Kalman filter, and include non-gravitational perturbations due to outgassing. Comparisons between observatories in several different circular heliocentric orbits show that observatories in orbits with radii less than 1 AU result in increased orbit determination accuracy for short tracking durations due to increased parallax per unit time. However, an observatory at 1 AU will perform similarly if the tracking duration is increased, and accuracy is significantly improved if additional observatories are positioned at the Sun-Earth Lagrange points L3, L4, or L5. A single observatory at 1 AU capable of both optical and range measurements yields the highest orbit determination accuracy in the shortest amount of time when compared to other systems of observatories.

Kay-Bunnell, Linda

2004-01-01

64

Nuclear reactor power for an electrically powered orbital transfer vehicle  

SciTech Connect

To help determine the systems requirements for a 300-kWe space nuclear reactor power system, a mission and spacecraft have been examined which utilize electric propulsion and this nuclear reactor power for multiple transfers of cargo between low Earth orbit (LEO) and geosynchronous Earth orbit (GEO). A propulsion system employing ion thrusters and xenon propellant was selected. Propellant and thrusters are replaced after each sortie to GEO. The mass of the Orbital Transfer Vehicle (OTV), empty and dry, is 11,000 kg; nominal propellant load is 5000 kg. The OTV operates between a circular orbit at 925 km altitude, 28.5 deg inclination, and GEO. Cargo is brought to the OTV by Shuttle and an Orbital Maneuvering Vehicle (OMV); the OTV then takes it to GEO. The OTV can also bring cargo back from GEO, for transfer by OMV to the Shuttle. OTV propellant is resupplied and the ion thrusters are replaced by the OMV before each trip to GEO. At the end of mission life, the OTV's electric propulsion is used to place it in a heliocentric orbit so that the reactor will not return to Earth. The nominal cargo capability to GEO is 6000 kg with a transit time of 120 days; 1350 kg can be transferred in 90 days, and 14,300 kg in 240 days. These capabilities can be considerably increased by using separate Shuttle launches to bring up propellant and cargo, or by changing to mercury propellant.

Jaffe, L.; Beatty, R.; Bhandari, P.; Chow, E.; Deininger, W.; Ewell, R.; Fujita, T.; Grossman, M.; Kia, T.; Nesmith, B.

1987-01-01

65

Five new and three improved mutual orbits of transneptunian binaries  

NASA Astrophysics Data System (ADS)

We present three improved and five new mutual orbits of transneptunian binary systems (58534) Logos-Zoe, (66652) Borasisi-Pabu, (88611) Teharonhiawako-Sawiskera, (123509) 2000 WK 183, (149780) Altjira, 2001 QY 297, 2003 QW 111, and 2003 QY 90 based on Hubble Space Telescope and Keck II laser guide star adaptive optics observations. Combining the five new orbit solutions with 17 previously known orbits yields a sample of 22 mutual orbits for which the period P, semimajor axis a, and eccentricity e have been determined. These orbits have mutual periods ranging from 5 to over 800 days, semimajor axes ranging from 1600 to 37,000 km, eccentricities ranging from 0 to 0.8, and system masses ranging from 2 × 10 17 to 2 × 10 22 kg. Based on the relative brightnesses of primaries and secondaries, most of these systems consist of near equal-sized pairs, although a few of the most massive systems are more lopsided. The observed distribution of orbital properties suggests that the most loosely-bound transneptunian binary systems are only found on dynamically cold heliocentric orbits. Of the 22 known binary mutual orbits, orientation ambiguities are now resolved for 9, of which 7 are prograde and 2 are retrograde, consistent with a random distribution of orbital orientations, but not with models predicting a strong preference for retrograde orbits. To the extent that other perturbations are not dominant, the binary systems undergo Kozai oscillations of their eccentricities and inclinations with periods of the order of tens of thousands to millions of years, some with strikingly high amplitudes.

Grundy, W. M.; Noll, K. S.; Nimmo, F.; Roe, H. G.; Buie, M. W.; Porter, S. B.; Benecchi, S. D.; Stephens, D. C.; Levison, H. F.; Stansberry, J. A.

2011-06-01

66

Orbital Debris  

NASA Technical Reports Server (NTRS)

Earth orbital debris issues and recommended future activities are discussed. The workshop addressed the areas of environment definition, hazards to spacecraft, and space object management. It concluded that orbital debris is a potential problem for future space operations. However, before recommending any major efforts to control the environment, more data are required. The most significant required data are on the population of debris smaller than 4 cm in diameter. New damage criteria are also required. When these data are obtained, they can be combined with hypervelocity data to evaluate the hazards to future spacecraft. After these hazards are understood, then techniques to control the environment can be evaluated.

Kessler, D. J. (compiler); Su, S. Y. (compiler)

1985-01-01

67

Preliminary Optimal Orbit Design for the Laser Interferometer Space Antenna (LISA)  

NASA Technical Reports Server (NTRS)

In this paper we present a preliminary optimal orbit analysis for the Laser Interferometer Space Antenna (LISA). LISA is a NASA/ESA mission to study gravitational waves and test predictions of general relativity. The nominal formation consists of three spacecraft in heliocentric orbits at 1 AU and trailing the Earth by twenty degrees. This configuration was chosen as a trade off to reduce the noise sources that will affect the instrument and to reduce the fuel to achieve the final orbit. We present equations for the nominal orbit design and discuss several different measures of performance for the LISA formation. All of the measures directly relate the formation dynamics to science performance. Also, constraints on the formation dynamics due to spacecraft and instrument limitations are discussed. Using the nominal solution as an initial guess, the formation is optimized using Sequential Quadratic Programming to maximize the performance while satisfying a set of nonlinear constraints. Results are presented for each of the performance measures.

Hughes, Steven P.; Bauer, Frank H. (Technical Monitor)

2002-01-01

68

Orbit extrapolation  

Microsoft Academic Search

Orbit extrapolation problems are considered for the following examples: the ARGOS satellite, the SPOT satellite, the D2B and Signe 3 satellites, the Laser satellites, the Transit satellites, and Skylab atmospheric entry. Various extrapolation methods are then described, including analytical (integration and transformation) methods, numerical integration methods (e.g., the Adams-Moulton, Cowell method), and the centering method.

N. Borderies

1980-01-01

69

Mars Orbit  

NSDL National Science Digital Library

This geometry lesson from Illuminations uses the model of the orbits of Mars and Earth relative to the sun to illustrate parametric equations. As an interdisciplinary learning activity, the material may be used in conjunction with astronomy lessons. An interactive applet and student questions are also included. The material is intended for grades 9-12 and should require 1 class period to complete.

2010-12-14

70

Orbital Elements  

NSDL National Science Digital Library

Coordinates for tracking the International Space Station and the Mir Space Station are available here from NASA's Johnson Space Center Flight Design and Dynamics Division. The Orbital Elements page offers real-time data for use in ground track plotting programs. The site cautions the data are for ground track plotting programs only and "should not be used for precise applications or analysis!"

71

Elliptical Orbits  

NSDL National Science Digital Library

Although not inquiry, this activity is important for students to understand what an ellipse is and what a focus is, and to break misconceptions about Earth's orbit being highly elliptical. This is the perfect place to check to see if students have the mis

Horton, Michael

2009-05-30

72

Orbital Effects on Mercury's Escaping Sodium Exosphere  

NASA Technical Reports Server (NTRS)

We present results from coronagraphic imaging of Mercury's sodium tail over a 7 deg field of view. Several sets of observations made at the McDonald Observatory since May 2007 show a tail of neutral sodium atoms stretching more than 1000 Mercury radii (R(sub m)) in length, or a full degree of sky. However, no tail was observed extending beyond 120 R(sub m) during the January 2008 MESSENGER Fly-by period, or during a similar orbital phase of Mercury in July 2008. Large changes in Mercury's heliocentric radial velocity cause Doppler shifts about the Fraunhofer absorption features; the resultant change in solar flux and radiation pressure is the primary cause of the observed variation in tail brightness. Smaller fluctuations in brightness may exist due to changing source rates at the surface, but we have no explicit evidence for such changes in this data set. The effects of radiation pressure on Mercury's escaping atmosphere are investigated using seven observations spanning different orbital phases. Total escape rates of atmospheric sodium are estimated to be between 5 and 13 x 10(exp 23) atoms/s and show a correlation to radiation pressure. Candidate sources of Mercury's sodium exosphere include desorption by UV sunlight, thermal desorption, solar wind channeled along Mercury's magnetic field lines, and micro-meteor impacts. Wide-angle observations of the full extent of Mercury's sodium tail offer opportunities to enhance our understanding of the time histories of these source rates.

Schmidt, Carl A.; Wilson, Jody K.; Baumgardner, Jeffrey; Mendillo, Michael

2009-01-01

73

Öpik-type collision probability for high-inclination orbits  

NASA Astrophysics Data System (ADS)

The classical Öpik theory provides an estimate of the collision probability between two bodies on bound, heliocentric or planetocentric orbits under restrictive assumptions of: (i) constant eccentricity and inclination, and (ii) uniform circulation of the longitude of node and argument of pericenter. These assumptions are violated whenever either of the orbits has a large inclination with respect to the local Laplace plane or large eccentricity, and their motion is perturbed by an exterior (tidal) gravitational field of a planet or the Sun. In this situation, known as the Lidov-Kozai regime, the eccentricity and inclination values exhibit large and correlated oscillations. At the same time, the longitude of node and the argument of pericenter may have strongly nonlinear time evolution, with the latter being even bound to a small interval of values. Here we develop a new Öpik-type collision probability theory which is valid even for highly inclined and/or eccentric orbits of the projectile. We assume that the orbit of the target is circular and in the local Laplace plane. Such a generalized setting is necessary, as an example, to correctly estimate the terrestrial impact fluxes of sporadic micrometeoroids on high-inclination orbits (notably those from the toroidal source and the associated helion and anti-helion arcs).

Vokrouhlický, David; Pokorný, Petr; Nesvorný, David

2012-05-01

74

Orbital Evolution and Migration of Giant Planets: Modeling Extrasolar Planets  

E-print Network

Giant planets in circumstellar disks can migrate inward from their initial (formation) positions. Radial migration is caused by inward torques between the planet and the disk; by outward torques between the planet and the spinning star; and by outward torques due to Roche lobe overflow and consequent mass loss from the planet. We present self-consistent numerical considerations of the problem of migrating giant planets. Summing torques on planets for various physical parameters, we find that Jupiter-mass planets can stably arrive and survive at small heliocentric distances, thus reproducing observed properties of some of the recently discovered extra-solar planets. Inward migration timescales can be approximately equal to or less than disk lifetimes and star spindown timescales. Therefore, the range of fates of massive planets is broad, and generally comprises three classes: (I) planets which migrate inward too rapidly and lose all their mass; (II) planets which migrate inward, lose some but not all of their mass, and survive in very small orbits; and (III) planets which do not lose any mass. Some planets in Class III do not migrate very far from their formation locations. Our results show that there is a wide range of possible fates for Jupiter-mass planets for both final heliocentric distance and final mass.

D. E. Trilling; W. Benz; T. Guillot; J. I. Lunine; W. B. Hubbard; A. Burrows

1998-01-28

75

Eye and orbit ultrasound  

MedlinePLUS

Echography - eye orbit; Ultrasound - eye orbit; Ocular ultrasonography; Orbital ultrasonography ... ophthalmology department of a hospital or clinic. Your eye is numbed with medicine (anesthetic drops). The ultrasound ...

76

Materials co-orbiting with known NEO asteroids: Properties inferred from collision-produced dust clouds  

NASA Astrophysics Data System (ADS)

Materials co-orbiting with Near-Earth Objects (NEOs) can be potentially hazardous when their diameters are of tens of meters. Such co-orbiting material is produced when small meteoroids about several meters in diameter collide with parent bodies of much larger diameters. These materials will be dispersed in orbits around the associated NEOs, and therefore could enter the terrestrial atmosphere even when their ‘parent’ NEOs miss the Earth. However, due to the small dimensions of these materials, they are hard to discover by traditional surveys. The co-orbiting materials collide regularly with smaller interplanetary objects, since the smaller objects are quite numerous. The dust cloud released in the collisions, containing fine-sized particles, becomes charged and can perturb the ambient solar wind. The resultant interplanetary magnetic field structure is called interplanetary field enhancement (IFE) and can be detected by magnetometers carried by interplanetary spacecraft as the dust cloud is swept outward by the solar wind. We use the records of IFE occurrence to trace interplanetary collisions and thus identify co-orbiting materials of well-known NEOs with ecliptic plane crossing near to or inside the Earth’s orbit. We suggest that co-orbiting materials of asteroid 138175, whose descending node is inside Earth’s orbit at heliocentric ecliptic longitude of 206 ?, should be responsible for at least some IFEs detected in the longitude range between 195 ? and 225 ?. The mass and spatial distributions of the potentially associated IFEs indicate that these co-orbiting materials had diameters of tens of meters before the collisions and had significant dispersion about the asteroid’s orbit. We can apply this technique to inventory the co-orbiting materials of other known NEOs and obtain the number density, orbits and sizes distributions of the materials. Thus we can estimate their impact probability and issue alerts when the Earth approaches the orbits of the hazardous objects.

Russell, C. T.; Wei, Hanying; Connors, Martin; Lai, Hairong; Delzanno, Gian Luca

77

Shapes of d Orbitals  

NSDL National Science Digital Library

Shapes of d Orbitals shows the d orbitals in an axis set. Running the mouse over an orbital reveals the "name" of that orbital. This is good practice for helping students link the name of an orbital to the orientation.Shapes of d Orbitals has a link to D Orbitals in an Octahedral Ligand Field. Here the user may click on the name of any one of the d orbitals to obtain a larger 3-dimensional image. The images are rotatable and scalable. Orbital phase is shown by the different colors.

78

Early orbit determination  

Microsoft Academic Search

Orbit determination for near real time monitoring of satellite movement based on limited observations is discussed. For geostationary satellites this early orbit determination requirement arises after injection into geostationary transfer orbit, apogee motor firing, and larger orbit maneuvers during the on-station phase. Early orbit determination is hampered by the limited amount of data caused by nonavailability of the tracking system.

S. Pallaschke

1986-01-01

79

ERS orbit control  

NASA Astrophysics Data System (ADS)

The European remote sensing mission orbit control is addressed. For the commissioning phase, the orbit is defined by the following requirements: Sun synchronous, local time of descending node 10:30; three days repeat cycle with 43 orbital revolutions; overhead Venice tower (12.508206 deg east, 45.314222 deg north). The launch, maneuvers for the initial acquisition of the operational orbit, orbit maintenance maneuvers, evaluation of the orbit control, and the drift of the inclination are summarized.

Rosengren, Mats

1991-12-01

80

On the Milankovitch orbital elements for perturbed Keplerian motion  

NASA Astrophysics Data System (ADS)

We consider sets of natural vectorial orbital elements of the Milankovitch type for perturbed Keplerian motion. These elements are closely related to the two vectorial first integrals of the unperturbed two-body problem; namely, the angular momentum vector and the Laplace-Runge-Lenz vector. After a detailed historical discussion of the origin and development of such elements, nonsingular equations for the time variations of these sets of elements under perturbations are established, both in Lagrangian and Gaussian form. After averaging, a compact, elegant, and symmetrical form of secular Milankovitch-like equations is obtained, which reminds of the structure of canonical systems of equations in Hamiltonian mechanics. As an application of this vectorial formulation, we analyze the motion of an object orbiting about a planet (idealized as a point mass moving in a heliocentric elliptical orbit) and subject to solar radiation pressure acceleration (obeying an inverse-square law). We show that the corresponding secular problem is integrable and we give an explicit closed-form solution.

Rosengren, Aaron J.; Scheeres, Daniel J.

2014-03-01

81

Working With Orbits  

NSDL National Science Digital Library

This site offers two programs to illustrate how orbits work. The Orbital Elements calculator contains animations to see how the appearance of an orbit depends on the values of the orbital elements which include distance from the Sun, eccentricity, pericenter location and anomaly. This is available in two or three dimensions. The Solar System allows users to watch several planets in our Solar System simultaneously orbit the Sun. An additional object (asteroid or comet) is present and users change the orbital parameters to see what types of orbits are possible for this object.

Hamilton, Douglas

82

Lunar Reconnaissance Orbiter Orbit Determination Accuracy Analysis  

NASA Technical Reports Server (NTRS)

Results from operational OD produced by the NASA Goddard Flight Dynamics Facility for the LRO nominal and extended mission are presented. During the LRO nominal mission, when LRO flew in a low circular orbit, orbit determination requirements were met nearly 100% of the time. When the extended mission began, LRO returned to a more elliptical frozen orbit where gravity and other modeling errors caused numerous violations of mission accuracy requirements. Prediction accuracy is particularly challenged during periods when LRO is in full-Sun. A series of improvements to LRO orbit determination are presented, including implementation of new lunar gravity models, improved spacecraft solar radiation pressure modeling using a dynamic multi-plate area model, a shorter orbit determination arc length, and a constrained plane method for estimation. The analysis presented in this paper shows that updated lunar gravity models improved accuracy in the frozen orbit, and a multiplate dynamic area model improves prediction accuracy during full-Sun orbit periods. Implementation of a 36-hour tracking data arc and plane constraints during edge-on orbit geometry also provide benefits. A comparison of the operational solutions to precision orbit determination solutions shows agreement on a 100- to 250-meter level in definitive accuracy.

Slojkowski, Steven E.

2014-01-01

83

Fibrolipoma of the orbit.  

PubMed

A 47-year-old woman presented with a growing mass on the lateral rim of orbit. Orbital CT revealed a well-circumscribed soft tissue mass in the right lateral orbit, with focal hyperostosis of the adjacent zygomatic bone. MRI showed a lesion of mixed T1-signal intensity, which became hypointense after fat suppression. The lesion was excised, and the diagnosis of orbital fibrolipoma was made by histopathologic examination. There was no evidence of tumor after 12 months of follow-up. Orbital fibrolipoma is a rare variant of lipoma, with only 1 case described previously. It should be considered in the differential diagnosis of orbital mass. PMID:20700070

Kim, Myung Hun; Sa, Ho Seok; Woo, Kyung; Kim, Yoon-Duck

2011-01-01

84

Transneptunian Orbit Computation  

NASA Astrophysics Data System (ADS)

We review the orbit computation problem for the transneptunian population. For these distant objects, the problem is characterized by their short observed orbital arcs, which are known to be coupled with large uncertainties in orbital elements. Currently, the observations of even the best observed objects, such as the first-ever transneptunian object (TNO), Pluto, cover only a fraction of their revolution. Furthermore, of the some 1200 objects discovered since 1992, roughly half have observations from only one opposition. To ensure realistic analyses of the population, e.g., in the derivation of unbiased orbital distributions or correlations between orbital and physical properties, realistic estimation of orbital uncertainties is important. We describe the inverse problem of orbit computation, emphasizing the short-arc problem and its statistical treatment. The complete solution to the problem can be given in terms of the orbital-element probability density function (p.d.f.), which then serves as a starting point for any further analysis, where knowledge of orbital uncertainties is required. We give an overview of the variety of computational techniques developed for TNO orbital uncertainty estimation in the recent years. After presenting the current orbital distribution, we demonstrate their application to several prediction problems, such as classification, ephemeris prediction, and dynamical analysis of objects. We conclude with some future prospects for TNO orbit computation concerning the forthcoming next-generation surveys, including the anticipated evolution of TNO orbital uncertainties over the coming decades.

Virtanen, J.; Tancredi, G.; Bernstein, G. M.; Spahr, T.; Muinonen, K.

85

Lunar orbiting prospector  

NASA Technical Reports Server (NTRS)

One of the prime reasons for establishing a manned lunar presence is the possibility of using the potential lunar resources. The Lunar Orbital Prospector (LOP) is a lunar orbiting platform whose mission is to prospect and explore the Moon from orbit in support of early lunar colonization and exploitation efforts. The LOP mission is divided into three primary phases: transport from Earth to low lunar orbit (LLO), operation in lunar orbit, and platform servicing in lunar orbit. The platform alters its orbit to obtain the desired surface viewing, and the orbit can be changed periodically as needed. After completion of the inital remote sensing mission, more ambitious and/or complicated prospecting and exploration missions can be contemplated. A refueled propulsion module, updated instruments, or additional remote sensing packages can be flown up from the lunar base to the platform.

1988-01-01

86

Rock-Around Orbits  

E-print Network

. . . . . . . . . . . . . 8 D. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 E. Minimum Distance . . . . . . . . . . . . . . . . . . . . . . 15 III ELLIPTICAL TARGET ORBITS : : : : : : : : : : : : : : : : : 18 A. Acceptable and Compatible Orbits... . . . . . . . . . . . . . 18 B. Eccentricity and Inclination Bounds . . . . . . . . . . . . . 19 C. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 D. Minimum Distance . . . . . . . . . . . . . . . . . . . . . . 26 IV J2 PERTURBATIONS...

Bourgeois, Scott K.

2010-07-14

87

Orbit CT scan  

MedlinePLUS

Massoud TF, Cross JJ. The orbit. In: Adam A, Dixon A, eds. Grainger and Allison's Diagnostic Radiology. 5th ed. Philadelphia, Pa: Elsevier Saunders; 2008:chap 61. Szatmary G. Imaging of the orbit. Neurol Clin . 2008;27:251-284.

88

Preliminary orbital parallax catalog  

NASA Technical Reports Server (NTRS)

The study is undertaken to calibrate the more reliable parallaxes derived from a comparison of visual and spectroscopic orbits and to encourage observational studies of other promising binaries. The methodological techniques used in computing orbital parallaxes are analyzed. Tables summarizing orbital data and derived system properties are then given. Also given is a series of detailed discussions of the 71 individual systems included in the tables. Data are listed for 57 other systems which are considered promising candidates for eventual orbital parallax determination.

Halliwell, M.

1981-01-01

89

Cosmetic orbital surgery  

Microsoft Academic Search

PurposeCurrent indications for orbital surgery primarily aimed at improving cosmesis are considered in the context of subspecialist orbital practice by an ophthalmologist.ScopeThyroid eye disease, orbital vascular anomalies, and dermolipomas are common orbital diseases in which the symptoms can be purely cosmetic. Accurate anatomical awareness, preoperative scanning, control of medical factors including smoking and thyroid status, and endoscopic techniques have all

2006-01-01

90

Mars orbit selection  

NASA Technical Reports Server (NTRS)

Parking orbits for a manned Mars mission are examined for ease of access to the Martian moons. Delta V plots for a variety of burns versus elliptical orbit apoapsis are included. A high elliptical orbit (24 hour period, 500 km periapsis, 20 to 30 deg. inclination) minimizes delta V to the Martian moons and Mars orbit insertion (MOI) and trans-Earth injection (TEI) delta Vs.

Babb, Gus R.; Stump, William R.

1986-01-01

91

Orbiting Binary Stars  

NSDL National Science Digital Library

This simulation demonstrates the path of binary stars' orbit. The user is able to set the masses, orbital separation, orbital eccentricity, the inclination angle to our line of sight, and the angle of the nodes of two orbiting stars. The observed velocities of the two stars, and the Doppler shifted spectral lines are also shown in the upper right box. The site also includes definitions of terms used, instructions on how to use the simulation and a few examples.

Kolena, John

2007-12-11

92

Five Equivalent d Orbitals  

ERIC Educational Resources Information Center

Amplifies and clarifies a previous paper on pyramidal d orbitals. Discusses two sets of pyramid d orbitals with respect to their maximum bond strength and their symmetry. Authors described the oblate and prolate pentagonal antiprisms arising from the two sets of five equivalent d orbitals. (RR)

Pauling, Linus; McClure, Vance

1970-01-01

93

Mars Reconnaissance Orbiter  

NSDL National Science Digital Library

This is the mission web site for the Mars Reconnaissance Orbiter, which went into orbit around Mars on March 10, 2006. The site provides links to updates and information about the project. The site features links to Mars Reconnaissance Orbiter images, animations, and datasets. Science operations commence in November, 2006.

Laboratory, Jet P.; Administration, National A.

94

SEASAT B orbit synthesis  

NASA Technical Reports Server (NTRS)

Addition were made to Battelle's Interactive Graphics Orbit Selection (IGOS) program; IGOS was exercised via telephone lines from JPL, and candidate SEASAT orbits were analyzed by Battelle. The additions to the program enable clear understanding of the implications of a specific orbit to the diverse desires of the SEASAT user community.

Rea, F. G.; Warmke, J. M.

1976-01-01

95

OTV orbital tanking systems  

NASA Technical Reports Server (NTRS)

Orbital transfer of cryogenic propellants could benefit spacecraft and Orbital Transfer Vehicle (OTV) missions in the 1980s by supplying main propulsion, attitude control, or other fluid systems. The Space Shuttle can operate as a tanker when equipped with cryogenic propellant storage and orbital transfer systems. The key technologies are multilayer insulation, capillary propellant acquisition, zero-g gaging, orbital chilldown, and possibly large flight weight dewars. The technologies and operations could be realistically demonstrated using a Centaur that has been integrated with the Shuttle. Orbital refueling capability can enhance the usefulness of the whole Shuttle program

Heald, D. A.; Merino, F.

1979-01-01

96

Lunar Reconnaissance Orbiter Orbit Determination Accuracy Analysis  

NASA Technical Reports Server (NTRS)

LRO definitive and predictive accuracy requirements were easily met in the nominal mission orbit, using the LP150Q lunar gravity model. center dot Accuracy of the LP150Q model is poorer in the extended mission elliptical orbit. center dot Later lunar gravity models, in particular GSFC-GRAIL-270, improve OD accuracy in the extended mission. center dot Implementation of a constrained plane when the orbit is within 45 degrees of the Earth-Moon line improves cross-track accuracy. center dot Prediction accuracy is still challenged during full-Sun periods due to coarse spacecraft area modeling - Implementation of a multi-plate area model with definitive attitude input can eliminate prediction violations. - The FDF is evaluating using analytic and predicted attitude modeling to improve full-Sun prediction accuracy. center dot Comparison of FDF ephemeris file to high-precision ephemeris files provides gross confirmation that overlap compares properly assess orbit accuracy.

Slojkowski, Steven E.

2014-01-01

97

Chemguide: Atomic Orbitals  

NSDL National Science Digital Library

This web page explains what atomic orbitals are in a way that makes it appropriate for pre-college introductory chemistry or physics courses. It goes into detail on s and p orbitals, including their shapes and energies, while devoting less discussion to d and f orbitals. The author uses an analogy comparing an atom to a multi-story house -- with the nucleus on the ground floor and then various rooms (orbitals) on the higher floors occupied by the electrons. A full page debunks the misconception that "orbitals" are like "orbits" (common among beginning students). Beyond this foundation, the tutorial explores how electrons fill orbitals (from low-to-high energy). It concludes with a set of questions, with answers provided, for self-gauging understanding. This page is part of Chemguide, an informational website developed by a veteran high school teacher to promote deeper understanding of concepts in introductory and intermediate-level chemistry.

Clark, Jim

2013-02-20

98

What do the orbital motions of the outer planets of the Solar System tell us about the Pioneer anomaly?  

E-print Network

In this paper we investigate the effects that an anomalous acceleration as that experienced by the Pioneer spacecraft after they passed the 20 AU threshold would induce on the orbital motions of the Solar System planets placed at heliocentric distances of 20 AU or larger as Uranus, Neptune and Pluto. It turns out that such an acceleration, with a magnitude of 8.74\\times 10^-10 m s^-2, would affect their orbits with secular and short-period signals large enough to be detected according to the latest published results by E.V. Pitjeva, even by considering errors up to 30 times larger than those released. The absence of such anomalous signatures in the latest data rules out the possibility that in the region 20-40 AU of the Solar System an anomalous force field inducing a constant and radial acceleration with those characteristics affects the motion of the major planets.

Lorenzo Iorio; Giuseppe Giudice

2006-01-14

99

Orbit Determination of the Lunar Reconnaissance Orbiter  

NASA Technical Reports Server (NTRS)

We present the results on precision orbit determination from the radio science investigation of the Lunar Reconnaissance Orbiter (LRO) spacecraft. We describe the data, modeling and methods used to achieve position knowledge several times better than the required 50-100m (in total position), over the period from 13 July 2009 to 31 January 2011. In addition to the near-continuous radiometric tracking data, we include altimetric data from the Lunar Orbiter Laser Altimeter (LOLA) in the form of crossover measurements, and show that they strongly improve the accuracy of the orbit reconstruction (total position overlap differences decrease from approx.70m to approx.23 m). To refine the spacecraft trajectory further, we develop a lunar gravity field by combining the newly acquired LRO data with the historical data. The reprocessing of the spacecraft trajectory with that model shows significantly increased accuracy (approx.20m with only the radiometric data, and approx.14m with the addition of the altimetric crossovers). LOLA topographic maps and calibration data from the Lunar Reconnaissance Orbiter Camera were used to supplement the results of the overlap analysis and demonstrate the trajectory accuracy.

Mazarico, Erwan; Rowlands, D. D.; Neumann, G. A.; Smith, D. E.; Torrence, M. H.; Lemoine, F. G.; Zuber, M. T.

2011-01-01

100

Curvature in orbital dynamics  

NASA Astrophysics Data System (ADS)

The physical basis and the geometrical significance of the equation for the orbit of a particle moving under the action of external forces is exhibited by deriving this equation in a coordinate-independent representation in terms of the radius of curvature of the orbit. Although this formulation appeared in Newton's Principia, it has been ignored in contemporary classical mechanics textbooks. For small eccentricities, the orbit equation is used to obtain approximate solutions that illustrate the role of curvature. It is shown that this approach leads to a simple graphical method for determining the orbits for central forces. This method is similar to one attributed to Newton, who applied it to a constant central force, and sent a diagram of the orbit to Hooke in 1679. The result is compared to the corresponding orbit of a ball revolving inside an inverted cone which Hooke described in his response to Newton.

Nauenberg, Michael

2005-04-01

101

Ghost orbit spectroscopy  

SciTech Connect

Direct periodic-orbit expansions of individual spectral eigenvalues is a new direction in quantum mechanics. Using a unitary S-matrix theory, we present exact, convergent, integral-free ghost orbit expansions of spectral eigenvalues for a step potential in the tunneling regime. We suggest an experiment to extract ghost orbit information from measured spectra in the tunneling regime (ghost orbit spectroscopy). We contrast our unitary, convergent theory with a recently published nonunitary, divergent theory [Yu. Dabaghian and R. Jensen, Eur. J. Phys. 26, 423 (2005)].

Bhullar, A. S.; Bluemel, R. [Department of Physics, Wesleyan University, Middletown, Connecticut 06459-0155 (United States); Koch, P. M. [Department of Physics and Astronomy, Stony Brook University, Stony Brook, New York 11794-3800 (United States)

2006-01-15

102

Magnetospheric Multiscale (MMS) Orbit  

NASA Video Gallery

This animation shows the orbits of Magnetospheric Multiscale (MMS) mission, a Solar-Terrestrial Probe mission comprising of four identically instrumented spacecraft that will study the Earth's magn...

103

Orbital Debris: A Chronology  

NASA Technical Reports Server (NTRS)

This chronology covers the 37-year history of orbital debris concerns. It tracks orbital debris hazard creation, research, observation, experimentation, management, mitigation, protection, and policy. Included are debris-producing, events; U.N. orbital debris treaties, Space Shuttle and space station orbital debris issues; ASAT tests; milestones in theory and modeling; uncontrolled reentries; detection system development; shielding development; geosynchronous debris issues, including reboost policies: returned surfaces studies, seminar papers reports, conferences, and studies; the increasing effect of space activities on astronomy; and growing international awareness of the near-Earth environment.

Portree, Davis S. F. (Editor); Loftus, Joseph P., Jr. (Editor)

1999-01-01

104

Titan Orbiter Aerorover Mission  

NASA Technical Reports Server (NTRS)

We propose a combined Titan orbiter and Titan Aerorover mission with an emphasis on both in situ and remote sensing measurements of Titan's surface, atmosphere, ionosphere, and magnetospheric interaction. The biological aspect of the Titan environment will be emphasized by the mission (i.e., search for organic materials which may include simple organics to 'amono' analogues of amino acids and possibly more complex, lightening detection and infrared, ultraviolet, and charged particle interactions with Titan's surface and atmosphere). An international mission is assumed to control costs. NASA will provide the orbiter, launch vehicle, DSN coverage and operations, while international partners will provide the Aerorover and up to 30% of the cost for the scientific instruments through collaborative efforts. To further reduce costs we propose a single PI for orbiter science instruments and a single PI for Aerorover science instruments. This approach will provide single command/data and power interface between spacecraft and orbiter instruments that will have redundant central DPU and power converter for their instruments. A similar approach could be used for the Aerorover. The mission profile will be constructed to minimize conflicts between Aerorover science, orbiter radar science, orbiter radio science, orbiter imaging science, and orbiter fields and particles (FP) science. Additional information is contained in the original extended abstract.

Sittler Jr., E. C.; Acuna, M.; Burchell, M. J.; Coates, A.; Farrell, W.; Flasar, M.; Goldstein, B. E.; Gorevan, S.; Hartle, R. E.; Johnson, W. T. K.

2001-01-01

105

Extrapolation of orbits  

Microsoft Academic Search

The use of analytic theory, numerical integration, or a mixed method in the extrapolation of a spacecraft orbit is shown to depend on mission requirements. Parameters to be extrapolated for the ARGOS satellite system, for SPOT satellite, DZB satellite, and for geostationary satellites are among examples cited. Orbit extrapolation for SKYLAB reentry is also covered. Analytic methods include integration of

N. Borderies

1980-01-01

106

Periodic orbits and stability  

Microsoft Academic Search

A review is presented of periodic orbits which are of interest to dynamical astronomy, and their relation to actual systems is considered. In particular, the paper reviews periodic orbits in planetary systems with two or more planets, in the asteroid system, in stellar systems, and in the motion of a star in various types of galaxies. Most systems are close

John D. Hadjidemetriou

1988-01-01

107

Orbital trapdoor fractures  

PubMed Central

Orbital trapdoor fractures are commonly encountered in children. Awareness of trapdoor fractures is of particular importance. This is because early recognition and treatment are necessary to prevent permanent motility abnormities. In this article, we will provide a brief overview of orbital fractures. The clinical and radiographic features of trapdoor fractures will then be reviewed, followed by a discussion on their proper management. PMID:23961006

Phan, Laura T.; Jordan Piluek, W.; McCulley, Timothy J.

2012-01-01

108

Constraint Orbital Branching  

E-print Network

a group of strong constraints on which to base the orbital branching .... that maps each feasible solution onto a feasible solution of the same value. ... For a point z ? Z, the orbit of z under the action of the group ? is the set of all elements of Z to

2008-01-01

109

Orbital Shape Representations.  

ERIC Educational Resources Information Center

Discusses the use of orbital shapes for instructional purposes, emphasizing that differences between polar, contour, and three-dimensional plots must be made clear to students or misconceptions will occur. Also presents three-dimensional contour surfaces for the seven 4f atomic orbitals of hydrogen and discusses their computer generation. (JN)

Kikuchi, Osamu; Suzuki, Keizo

1985-01-01

110

Analyzing Shuttle Orbiter Trajectories  

NASA Technical Reports Server (NTRS)

LRBET4 program best-estimated-of-trajectory (BET) calculation for post-flight trajectory analysis of Shuttle orbiter. Produces estimated measurements for comparing predicted and actual trajectory of Earth-orbiting spacecraft. Kalman filter and smoothing filter applied to input data to estimate state vector, reduce noise, and produce BET. LRBET4 written in FORTRAN IV for batch execution.

Lear, W. M.

1986-01-01

111

Fibrolipoma of the orbit.  

PubMed

Herein we present a retrospective case report of a very rare fibrolipoma originating in the orbit. Lipomas and related variants presenting in the orbit are very rare. Only 2 documented orbital fibrolipomas were noted in our review of literature. A 26-year-old woman presented with a growing mass below the left eyebrow 4 years after suffering facial trauma after being kicked in the face by a horse. CT demonstrated a hypodense nodule adherent to the orbital portion of the left frontal bone that was not encapsulated. An elective left anterior orbitotomy with excisional biopsy was performed, and fibrolipoma was confirmed on histopathologic examination. There was no evidence of tumor after 2-year follow up. The presence of a fibrolipoma in the periosteum of the orbital rim is very rare and might be a result of inflammatory transformation following facial trauma. PMID:23392312

Ali, Sana F; Farber, Martha; Meyer, Dale R

2013-01-01

112

A search for asteroids on Earth horseshoe orbits  

NASA Astrophysics Data System (ADS)

There are currently about a dozen known near-Earth objects with well-determined orbits and semi-major axis between 0.99 and 1.01 AU (Ted Bowell's asteroid database, 2003). We examined their orbital trajectories using the Horizons integrator (Giorgini, 1996) in an effort to find asteroids on Earth horseshoe orbits. Two objects (2002 AA29 and 2000 PH5) displayed a recent abrupt reversal in the evolution of their ecliptic longitude with respect to that of Earth, indicating a classic horseshoe or tadpole behavior. In a Sun-centered frame co-rotating with Earth, their trajectory displays the horseshoe pattern with the expected libration period of ˜100 years. 2002 AA29 was previously recognized as being on a horseshoe trajectory (Connors et al., 2002). Wiegert et al. (2002) suggested that 2000 PH5 and 2001 GO2 are on horseshoe orbits, although their claim rests on a single 4.5-day observational arc for 2001 GO2. Although the mean longitude of 2000 PH5 always remains at least ˜25 degrees away from the longitude of Earth, the asteroid makes very close Earth approaches, within a few lunar distances. This is due to its significant ˜0.2 eccentricity and the corresponding epicycle-like motion that is superimposed on the libration in mean longitude. The fact that this object happens to have just the right eccentricity to bring it so close to Earth suggests that it may have been barely ejected from the Earth-Moon system into an heliocentric orbit. Goldstone radar observations conducted by JLM and collaborators show that the object does not appear to be man-made. Higher resolution observations with the Arecibo radar will be conducted in an attempt to constrain its plausible source region. Because of its peculiar origin, repeating close approaches to Earth, and low delta-V, this object may be an attractive target for a sample return mission. A long-lived transponder on its surface would also provide interesting dynamical information.

Margot, J. L.; Nicholson, P. D.

2003-08-01

113

Orbit Stabilization of Nanosat  

SciTech Connect

An algorithm is developed to control a pulsed {Delta}V thruster on a small satellite to allow it to fly in formation with a host satellite undergoing time dependent atmospheric drag deceleration. The algorithm uses four short thrusts per orbit to correct for differences in the average radii of the satellites due to differences in drag and one thrust to symmetrize the orbits. The radial difference between the orbits is the only input to the algorithm. The algorithm automatically stabilizes the orbits after ejection and includes provisions to allow azimuthal positional changes by modifying the drag compensation pulses. The algorithm gives radial and azimuthal deadbands of 50 cm and 3 m for a radial measurement accuracy of {+-} 5 cm and {+-} 60% period variation in the drag coefficient of the host. Approaches to further reduce the deadbands are described. The methodology of establishing a stable orbit after ejection is illustrated in an appendix. The results show the optimum ejection angle to minimize stabilization thrust is upward at 86{sup o} from the orbital velocity. At this angle the stabilization velocity that must be supplied by the thruster is half the ejection velocity. An ejection velocity of 0.02 m/sat 86{sup o} gives an azimuthal separation after ejection and orbit stabilization of 187 m. A description of liquid based gas thrusters suitable for the satellite control is included in an appendix.

JOHNSON,DAVID J.

1999-12-01

114

External Resource: What is orbit?  

NSDL National Science Digital Library

A 5-8 NASA Education reference answering the question, " What is orbit?" Topics include: satellite, ecliptic plane, perigee, apogee, escape velocity, geosynchronous, polar orbits, and low Earth orbit.

1900-01-01

115

Removal of orbital debris  

NASA Technical Reports Server (NTRS)

The several methods presently identified for the reduction of orbital debris populations are broadly classifiable as either preventive or remedial, and fall within distinctive operational regimes. For all particles, (1) in the 250-2000-km altitude band, intelligent sweepers may be used; (2) for large objects, in the 80-250-km altitude band, orbital decay renders removal impractical; (3) for the 250-750-km altitude band, deorbit devices should be used; (4) for 750-2500-km altitude, OMV rendezvous for propulsive deorbit package attachment is foreseeable; and beyond 2500 km, (5) propulsive escape from earth orbit is required.

Petro, Andrew J.; Talent, David L.

1989-01-01

116

Nontraumatic orbital hemorrhage.  

PubMed

Nontraumatic orbital hemorrhage (NTOH) is uncommon. I summarize the published reports of NTOH and offer a classification based on anatomic and etiologic factors. Anatomic patterns of NTOH include diffuse intraorbital hemorrhage, "encysted" hemorrhage (hematic cyst), subperiosteal hemorrhage, hemorrhage in relation to extraocular muscles, and hemorrhage in relation to orbital floor implants. Etiologic factors include vascular malformations and lesions, increased venous pressure, bleeding disorders, infection and inflammation, and neoplastic and nonneoplastic orbital lesions. The majority of NTOH patients can be managed conservatively, but some will have visual compromise and may require operative intervention. Some will suffer permanent visual loss, but a large majority have a good visual outcome. PMID:24359805

McNab, Alan A

2014-01-01

117

Orbit Determination Issues for Libration Point Orbits  

NASA Technical Reports Server (NTRS)

Libration point mission designers require knowledge of orbital accuracy for a variety of analyses including station keeping control strategies, transfer trajectory design, and formation and constellation control. Past publications have detailed orbit determination (OD) results from individual libration point missions. This paper collects both published and unpublished results from four previous libration point missions (ISEE (International Sun-Earth Explorer) -3, SOHO (Solar and Heliospheric Observatory), ACE (Advanced Composition Explorer) and MAP (Microwave Anisotropy Probe)) supported by Goddard Space Flight Center's Guidance, Navigation & Control Center. The results of those missions are presented along with OD issues specific to each mission. All past missions have been limited to ground based tracking through NASA ground sites using standard range and Doppler measurement types. Advanced technology is enabling other OD options including onboard navigation using seaboard attitude sensors and the use of the Very Long Baseline Interferometry (VLBI) measurement Delta Differenced One-Way Range (DDOR). Both options potentially enable missions to reduce coherent dedicated tracking passes while maintaining orbital accuracy. With the increased projected loading of the DSN (Deep Space Network), missions must find alternatives to the standard OD scenario.

Beckman, Mark; Bauer, Frank (Technical Monitor)

2002-01-01

118

Orbit Determination Issues for Libration Point Orbits  

NASA Technical Reports Server (NTRS)

Libration point mission designers require knowledge of orbital accuracy for a variety of analyses including station keeping control strategies, transfer trajectory design, and formation and constellation control. Past publications have detailed orbit determination (OD) results from individual notation point missions. This paper collects both published and unpublished results from four previous notation point missions (ISEE-3, SOHO, ACE and MAP) supported by Goddard Space Flight Center's Guidance, Navigation & Control Center. The results of those missions are presented along with OD issues specific to each mission. All past missions have been limited to ground based tracking through NASA ground sites using standard marine and Doppler measurement types. Advanced technology is enabling other OD options including onboard navigation using onboard attitude sensors and the use of the Very Long Baseline Interferometry (VLBI) measurement Delta Differenced One-Way Range (DDOR). Both options potentially enable missions to reduce coherent dedicated tracking passes while maintaining orbital accuracy. With the increased projected loading of the DSN, missions must find alternatives to the standard OD scenario.

Beckman, Mark; Bauer, Frank (Technical Monitor)

2002-01-01

119

The SIde-Looking Coronagraph for the solar orbiter mission: Optical and mechanical designs  

NASA Astrophysics Data System (ADS)

The SIde-Looking Coronagraph (SILC) is intented to be proposed as part of the payload of the Solar Orbiter mission of the European Space Agency. Solar Orbiter will follow elliptic orbits with a large range of heliocentric distance, from 0.21 to 0.6 AU, and will reach heliographic latitudes as high as 38°. Furthermore, the spacecraft will have an offset pointing capability so as to target any point of the solar disk. These characteristics, in addition to the severe thermal environment, are very restrictive for a coronagraph and lead us to propose an externally occulted coronagraph entirely protected from direct sunlight by remaining in the shadow of the spacecraft and looking sideways. The optical design follows the general principles of an externally occulted coronagraph adapted to the side-looking concept. Although SILC loses the full spatial coverage of the corona, it can observe the inner part of the corona (down to 1.5 solar radii) during the whole mission and compensate the off-pointing of the spacecraft. The optical and mechanical designs of SILC are presented in detail.

Vivès, S.; Lamy, P.; Guitton, J.; Boit, J. L.; Dargent, P.

120

The SIde-Looking Coronagraph (SILC) for the Solar Orbiter mission  

NASA Astrophysics Data System (ADS)

The SIde-Looking Coronagraph (SILC) is one of the solar remote-sensing instruments proposed for the payload of the Solar Orbiter mission (European Space Agency, ESA). The Solar Orbiter will describe elliptic orbits with a large range of heliocentric distance, from 0.21 to 0.6 AU, that is a factor 3 for the geometric conditions, and will reach heliographic latitudes as high as 38 degrees. Furthermore, the spacecraft will have offset pointing capability so as to target any point of the solar disk. These specificities (in addition to the severe thermal environment) are very restrictive for a coronagraph and lead us to propose an externally occulted coronagraph entirely protected from direct sunlight by remaining in the shadow of the spacecraft and looking sideways. The optical design follows the general principles of an externally-occulted coronagraph adapted to the side-looking concept. Although SILC loses the full spatial coverage of the corona, it can observe the inner part of the corona (down to 1.5 solar radii) during the whole mission and compensate the off-pointing of the spacecraft in the two directions. The performances, resulting from ray-tracing calculations, will be presented together with the first measurements of the stray light level.

Vives, S.; Lamy, P.; Korendyke, C.

121

The Tajikistan superbolide of July 23, 2008. I. Trajectory, orbit, and preliminary fall data  

NASA Astrophysics Data System (ADS)

The results of the atmospheric trajectory, radiant, heliocentric orbit, and preliminary strewn field calculations for an extremely bright slow-moving fireball are presented. In the evening hours of July 23, 2008, a bright object entered Earth's atmosphere over Tajikistan. The fireball had a -20.3 maximum absolute magnitude and a spectacularly long persistent dust trail remained visible over a widespread region of Tajikistan for about 28 minutes after sunset. The fireball was also recorded by a visible-light satellite system at 14 h 45 min 25 s UT, and the dust trail was imaged by video and photocameras. A unique aspect of this event is that it was detected by two infrasound and five seismic stations too. The bolide was first recorded at a height of 38.2 km, reached its maximum brightness at a height of 35.0 km, and finished at a height of 19.6 km. The first breakup occurred under an aerodynamic pressure of approximately 1.6 MPa, similar to the values derived for breakups of the scarcely reported meteorite-dropping bolides. The fireball's trajectory and dynamic results suggest that meteorite survival is likely. The meteoroid followed an Apollo-like asteroid orbit comparable to those derived for previously recovered meteorites with accurately known orbits.

Konovalova, Natalia A.; Madiedo, Jose M.; Trigo-Rodríguez, Josep M.

2013-12-01

122

Rotational Disruption of Comets with Parabolic Orbits  

NASA Astrophysics Data System (ADS)

One of the most fundamental problems in planetary science is the natural lifetime of comets, which is limited by several processes, most notably by spontaneous disruption of the nucleus. While the underlying mechanism is uncertain, rapid rotation is often suspected. To address this problem, I derived the probability of rotational disruption, and investigated it for comets with parabolic orbits as a function of perihelion distance and nucleus size for a range of input parameters. The disruption probability is defined as the ratio of expected change in the rotation rate to the allowable span of the rotation rate, the latter being limited by the critical rotation rate (prograde and retrograde), which I adopted from Davidsson (2001, Icarus 149, 375). The expected change in the rotation rate, resulting from the action of torques generated by mass loss, is calculated following the standard approach (e.g. Drahus et al. 2011, ApJL 734, L4, and ref. therein), but taking into account the suspected decrease of the net torque with an increasing active fraction of the nucleus (Jewitt 1997, EM&P 79, 35; Samarasinha & Mueller 2013, ApJL 775, L10). The sublimation flux is obtained from the standard energy balance equation (e.g. Cowan & A’Hearn 1979, M&P 21, 155), but I also take into account extinction of sunlight in the dust coma. I find that close to the Sun coma transmission steeply decreases with a decreasing heliocentric distance, resulting in the sublimation flux at a remarkably constant level, and also that coma transmission decreases with an increasing nucleus size, both properties being critically important in the calculation of sublimation flux for large sungrazers. The obtained rotational-disruption probability features several interesting properties. It has a well-defined regime occupied by smaller comets closely approaching the Sun, for which rotational disruption is unavoidable regardless of the original rotation state. Moreover, the probability function offers a very close match to the empirical survival cutoff for long-period comets with perihelia of less than 0.5 AU (Bortle 1991, ICQ 13, 89), independently suggesting that rotational disruption is the primary mechanism responsible for the destruction of comets.

Drahus, Michal

2014-11-01

123

Tethered orbital refueling study  

NASA Technical Reports Server (NTRS)

One of the major applications of the space station will be to act as a refueling depot for cryogenic-fueled space-based orbital transfer vehicles (OTV), Earth-storable fueled orbit maneuvering vehicles, and refurbishable satellite spacecraft using hydrazine. One alternative for fuel storage at the space station is a tethered orbital refueling facility (TORF), separated from the space station by a sufficient distance to induce a gravity gradient force that settles the stored fuels. The technical feasibility was examined with the primary focus on the refueling of LO2/LH2 orbital transfer vehicles. Also examined was the tethered facility on the space station. It was compared to a zero-gravity facility. A tethered refueling facility should be considered as a viable alternative to a zero-gravity facility if the zero-gravity fluid transfer technology, such as the propellant management device and no vent fill, proves to be difficult to develop with the required performance.

Fester, Dale A.; Rudolph, L. Kevin; Kiefel, Erlinda R.; Abbott, Peter W.; Grossrode, Pat

1986-01-01

124

Optical orbital debris spotter  

NASA Astrophysics Data System (ADS)

The number of man-made debris objects orbiting the Earth, or orbital debris, is alarmingly increasing, resulting in the increased probability of degradation, damage, or destruction of operating spacecraft. In part, small objects (<10 cm) in Low Earth Orbit (LEO) are of concern because they are abundant and difficult to track or even to detect on a routine basis. Due to the increasing debris population it is reasonable to assume that improved capabilities for on-orbit damage attribution, in addition to increased capabilities to detect and track small objects are needed. Here we present a sensor concept to detect small debris with sizes between approximately 1.0 and 0.01 cm in the vicinity of a host spacecraft for near real time damage attribution and characterization of dense debris fields and potentially to provide additional data to existing debris models.

Englert, Christoph R.; Bays, J. Timothy; Marr, Kenneth D.; Brown, Charles M.; Nicholas, Andrew C.; Finne, Theodore T.

2014-11-01

125

Orbiter entry aerothermodynamics  

NASA Technical Reports Server (NTRS)

The challenge in the definition of the entry aerothermodynamic environment arising from the challenge of a reliable and reusable Orbiter is reviewed in light of the existing technology. Select problems pertinent to the orbiter development are discussed with reference to comprehensive treatments. These problems include boundary layer transition, leeward-side heating, shock/shock interaction scaling, tile gap heating, and nonequilibrium effects such as surface catalysis. Sample measurements obtained from test flights of the Orbiter are presented with comparison to preflight expectations. Numerical and wind tunnel simulations gave efficient information for defining the entry environment and an adequate level of preflight confidence. The high quality flight data provide an opportunity to refine the operational capability of the orbiter and serve as a benchmark both for the development of aerothermodynamic technology and for use in meeting future entry heating challenges.

Ried, R. C.

1985-01-01

126

Imaging in orbital trauma  

PubMed Central

Orbital trauma is one of the most common reasons for ophthalmology specialty consultation in the emergency department setting. We survey the literature from 1990 to present to describe the role of computed tomography (CT), magnetic resonance imaging (MRI) and their associated angiography in some of the most commonly encountered orbital trauma conditions. CT orbit can often detect certain types of foreign bodies, lens dislocation, ruptured globe, choroidal or retinal detachments, or cavernous sinus thrombosis and thus complement a bedside ophthalmic exam that can sometimes be limited in the setting of trauma. CT remains the workhorse for acute orbital trauma owing to its rapidity and ability to delineate bony abnormalities; however MRI remains an important modality in special circumstances such as soft tissue assessment or with organic foreign bodies. PMID:23961028

Lin, Ken Y.; Ngai, Philip; Echegoyen, Julio C.; Tao, Jeremiah P.

2012-01-01

127

Mars parking orbit selection  

NASA Technical Reports Server (NTRS)

For a Mars mission, the selection of a parking orbit is greatly influenced by the precession caused by the oblateness of the planet. This affects the departure condition for earth return, and therefore, the mass required in LEO for a Mars mission. In this investigation, minimum LEO mass penalties were observed for parking orbits characterized by having near-equatorial inclinations, high eccentricities, and requiring a three-dimensional departure burn. However, because near-equatorial inclination orbits have poor planetary coverage characteristics, they are not desirable from a science viewpoint. To enhance these science requirements along with landing-site accessibility, a penalty in initial LEO mass is required. This study shows that this initial LEO mass penalty is reduced for orbits characterized with low to moderate eccentricities, nonequatorial inclinations, and a tangential periapsis arrival and departure burn.

Desai, Prasun N.; Braun, Robert D.

1990-01-01

128

Aerobraking orbital transfer vehicle  

NASA Technical Reports Server (NTRS)

An aerobraking orbital transfer vehicle which includes an aerobraking device which also serves as a heat shield in the shape of a raked-off elliptic or circular cone with a circular or elliptical base, and with an ellipsoid or other blunt shape nose. The aerobraking device is fitted with a toroid-like skirt and is integral with the support structure of the propulsion system and other systems of the space vehicle. The vehicle is intended to be transported in components to a space station in lower earth orbit where it is assembled for use as a transportation system from low earth orbit to geosynchronous earth orbit and return. Conventional guidance means are included for autonomous flight.

Scott, Carl D. (Inventor); Nagy, Kornel (Inventor); Roberts, Barney B. (Inventor); Ried, Robert C. (Inventor); Kroll, Kenneth R. (Inventor); Gamble, Joe (Inventor)

1989-01-01

129

Altimetry, Orbits and Tides  

NASA Technical Reports Server (NTRS)

The nature of the orbit error and its effect on the sea surface heights calculated with satellite altimetry are explained. The elementary concepts of celestial mechanics required to follow a general discussion of the problem are included. Consideration of errors in the orbits of satellites with precisely repeating ground tracks (SEASAT, TOPEX, ERS-1, POSEIDON, amongst past and future altimeter satellites) are detailed. The theoretical conclusions are illustrated with the numerical results of computer simulations. The nature of the errors in this type of orbits is such that this error can be filtered out by using height differences along repeating (overlapping) passes. This makes them particularly valuable for the study and monitoring of changes in the sea surface, such as tides. Elements of tidal theory, showing how these principles can be combined with those pertinent to the orbit error to make direct maps of the tides using altimetry are presented.

Colombo, O. L.

1984-01-01

130

ARTEMIS Orbits Magnetic Moon  

NASA Video Gallery

NASA's THEMIS spacecraft have completed their mission and are still working perfectly, so NASA is re-directing the outermost two spacecraft to special orbits around the Moon. Now called ARTEMIS, th...

131

Habitability study shuttle orbiter  

NASA Technical Reports Server (NTRS)

Studies of the habitability of the space shuttle orbiter are briefly summarized. Selected illustrations and descriptions are presented for: crew compartment, hygiene facilities, food system and galley, and storage systems.

1972-01-01

132

Indian Mars Orbiter Mission  

NASA Astrophysics Data System (ADS)

The Mars Orbiter Mission (MOM) is the first interplanetary mission of India launched by Indian Polar Satellite Launch Vehicle (PSLV-XL) on 5 November 2013. It departed from Earth's orbit on Dec. 1, 2013, on its 300-days journey to Mars. MOM will reach Mars on Sept. 24, 2014. The orbit of MOM around Mars is highly elliptical with periapsis ~370 km and apoapsis ~80000 km, inclination 151 degree, and orbital period 3.15 sols. The spacecraft mass is 1350 kg, with dry mass of 500 kg and science payload mass of 14 kg. The spacecraft carries five science payloads, namely: Methane Sensor for Mars (MSM), Mars Colour Camera (MCC), Lyman Alpha Photometer (LAP), Mars Exospheric Neutral Composition Analyzer (MENCA), TIR Imaging Spectrometer (TIS). This paper will present the details of the instruments, observation plan, and expected science.

Bhardwaj, Anil

133

Pediatric Orbital Fractures  

PubMed Central

It is wise to recall the dictum “children are not small adults” when managing pediatric orbital fractures. In a child, the craniofacial skeleton undergoes significant changes in size, shape, and proportion as it grows into maturity. Accordingly, the craniomaxillofacial surgeon must select an appropriate treatment strategy that considers both the nature of the injury and the child's stage of growth. The following review will discuss the management of pediatric orbital fractures, with an emphasis on clinically oriented anatomy and development. PMID:24436730

Oppenheimer, Adam J.; Monson, Laura A.; Buchman, Steven R.

2013-01-01

134

Satellites Orbiting Earth  

NSDL National Science Digital Library

In recent years, there has been a push to better understand how Earth works as a system- how land, oceans, air, and life all interact. Satellites in orbit around Earth are a fast and efficient way of gathering remotely sensed data about the planet as a whole. This animated video shows the orbital paths of the satellites in the National Aeronautics and Space Administration (NASA) Earth Observing System (EOS), a collection of satellites that work together to study Earth on a wide scale.

135

Orbital Dirofilariasis: MR Findings  

Microsoft Academic Search

Summary: Dirofilariasis is a helminthic zoonosis occurring in many parts of the world. We report the findings in a 61- year-old woman who had painless right exophthalmos caused by orbital dirofilariasis. A vivid worm was embed- ded inside an inflammatory nodule in the right orbit. On T1-weighted MR images, the parasite was visible as a dis- crete, low-intensity, tubular signal

Reinhard Groell; Gerhard Ranner; Martin M. Uggowitzer; Hannes Braun

136

A tapestry of orbits  

SciTech Connect

In this book, the author describes how orbital research developed to yield a rich harvest of knowledge about the earth and its atmosphere. King-Hele relates a personal account of this research based on analysis of satellite orbits between 1957 and 1990 conducted from the Royal Aircraft Establishment in Farnborough England. The early research methods used before the launch of Sputnik in 1957 are discussed.

King-Hele, D.

1992-01-01

137

The Lunar Orbital Prospector  

NASA Technical Reports Server (NTRS)

The establishment of lunar bases will not end the need for remote sensing of the lunar surface by orbiting platforms. Human and robotic surface exploration will necessarily be limited to some proximate distance from the support base. Near real-time, high-resolution, global characterization of the lunar surface by orbiting sensing systems will continue to be essential to the understanding of the Moon's geophysical structure and the location of exploitable minerals and deposits of raw materials. The Lunar Orbital Prospector (LOP) is an orbiting sensing platform capable of supporting a variety of modular sensing packages. Serviced by a lunar-based shuttle, the LOP will permit the exchange of instrument packages to meet evolving mission needs. The ability to recover, modify, and rotate sensing packages allows their reuse in varying combinations. Combining this flexibility with robust orbit modification capabilities and near real-time telemetry links provides considerable system responsiveness. Maintenance and modification of the LOP orbit are accomplished through use of an onboard propulsion system that burns lunar-supplied oxygen and aluminum. The relatively low performance of such a system is more than compensated for by the elimination of the need for Earth-supplied propellants. The LOP concept envisions a continuous expansion of capability through the incorporation of new instrument technologies and the addition of platforms.

Redd, Frank J.; Cantrell, James N.; Mccurdy, Greg

1992-01-01

138

Two Body Orbits Model  

NSDL National Science Digital Library

The Two Body Orbits model for teachers shows the motion of two objects (binary star or moon-planet system) interacting via Newton's law of universal gravitation. It is designed to teach physics, Earth science, and environmental science topics by showing the spatial path of objects around their common center of mass (barycenter). An optional 3D view shows the celestial sphere and and the orbital plane (ecliptic). Default units are chosen for Earth obit about our Sun so that the distance unit is one astronomical unit and the time unit is one year.   An important feature of the ready-to-run Two Body Orbits simulation is that it can be customized by teachers to meet various learning objectives. The teacher sets the ratio of the two masses, their initial positions and velocities, and various visualization and scale parameters. Documentation, such as an exercise or lesson, can be added to the simulation by entering a filename into the Customization dialog. Selecting the âstudentâ checkbox creates a ready-to-run package with the new configuration without the Customization dialog. The Two Body Orbits model was created using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run Java archive. Double clicking the ejs_mech_orbits_TwoBodyOrbits.jar file will run the program if Java is installed. EJS is a part of the Open Source Physics Project and is available in the OSP Collection.

Christian, Wolfgang

2012-07-18

139

Overall view of the Orbiter Servicing Structure within the Orbiter ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

Overall view of the Orbiter Servicing Structure within the Orbiter Processing Facility at Kennedy Space Center. Can you see any hint of the Orbiter Discovery? It is in there. - Space Transportation System, Orbiter Discovery (OV-103), Lyndon B. Johnson Space Center, 2101 NASA Parkway, Houston, Harris County, TX

140

Mars Geoscience Orbiter and Lunar Geoscience Orbiter  

NASA Technical Reports Server (NTRS)

The feasibility of using the AE/DE Earth orbiting spacecraft design for the LGO and/or MGO missions was determined. Configurations were developed and subsystems analysis was carried out to optimize the suitability of the spacecraft to the missions. The primary conclusion is that the basic AE/DE spacecraft can readily be applied to the LGO mission with relatively minor, low risk modifications. The MGO mission poses a somewhat more complex problem, primarily due to the overall maneuvering hydrazine budget and power requirements of the sensors and their desired duty cycle. These considerations dictate a modification (scaling up) of the structure to support mission requirements.

Fuldner, W. V.; Kaskiewicz, P. F.

1983-01-01

141

Sedna Orbit Comparisons  

NASA Technical Reports Server (NTRS)

These four panels show the location of the newly discovered planet-like object, dubbed 'Sedna,' which lies in the farthest reaches of our solar system. Each panel, moving counterclockwise from the upper left, successively zooms out to place Sedna in context. The first panel shows the orbits of the inner planets, including Earth, and the asteroid belt that lies between Mars and Jupiter. In the second panel, Sedna is shown well outside the orbits of the outer planets and the more distant Kuiper Belt objects. Sedna's full orbit is illustrated in the third panel along with the object's current location. Sedna is nearing its closest approach to the Sun; its 10,000 year orbit typically takes it to far greater distances. The final panel zooms out much farther, showing that even this large elliptical orbit falls inside what was previously thought to be the inner edge of the Oort cloud. The Oort cloud is a spherical distribution of cold, icy bodies lying at the limits of the Sun's gravitational pull. Sedna's presence suggests that this Oort cloud is much closer than scientists believed.

2004-01-01

142

Mars Reconnaissance Orbiter Aerobraking  

NASA Technical Reports Server (NTRS)

December 10, 2003

NASA's Mars Reconnaissance Orbiter dips into the thin martian atmosphere to adjust its orbit in this artist's concept illustration.

NASA plans to launch this multipurpose spacecraft in August 2005 for arrival at Mars in March 2006. The plans call for controlled use of atmospheric friction in a process called aerobraking for about six months after arrival to change the initial, very elongated orbit into a rounder shape optimal for science operations.

Mars Reconnaissance Orbiter is designed to advance our understanding of Mars through detailed observation, to examine potential landing sites for future surface missions and to provide a high-data-rate communications relay for those missions.

NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology, Pasadena, manages the Mars Reconnaissance Orbiter Project for the NASA Office of Space Science, Washington. JPL's main industrial partner in the project, Lockheed Martin Space Systems, Denver, Colo., is building the spacecraft.

2003-01-01

143

Primary orbital extraskeletal osteosarcoma.  

PubMed

The authors describe a case of orbital extraskeletal osteosarcoma. A 78-year-old man with a history of rheumatoid arthritis on long-term corticosteroids had a left medial canthal basal cell carcinoma excision followed by adjuvant radiotherapy. Twelve months later, he re-presented with a large rapidly-growing calcified mass involving his left medial canthus and orbit. An incisional biopsy demonstrated an infiltrate of atypical cells exhibiting mitotic activity with a rosette arrangement around partially calcified necrotic tissue. The patient underwent orbital exenteration and a partial maxillectomy. Histopathology demonstrated an extraskeletal osteosarcoma. It is extremely rare for this tumor to occur in the orbit. Immunosuppression and adjuvant radiotherapy were possible predisposing factors in the development of this tumor. Extraskeletal osteosarcoma (ESOS) is a malignant tumour that produces osteoid. It develops in soft tissue without continuity to bone or periosteum. It is rare and comprises fewer than 5% of all osteosarcomas. Extraskeletal osteosarcoma primarily affects patients above 50 years of age and has a poor prognosis. In this report, we describe the clinical, radiologic, and pathologic records of a rare case of primary ESOS of the orbit. PMID:22132847

Fan, Jennifer C; Lamont, Duncan L; Greenbaum, Adam R; Ng, Stephen G J

2011-12-01

144

Helioseismology with Solar Orbiter  

E-print Network

The Solar Orbiter mission, to be launched in July 2017, will carry a suite of remote sensing and in-situ instruments, including the Polarimetric and Helioseismic Imager (PHI). PHI will deliver high-cadence images of the Sun in intensity and Doppler velocity suitable for carrying out novel helioseismic studies. The orbit of the Solar Orbiter spacecraft will reach a solar latitude of up to 21 deg (up to 34 deg by the end of the extended mission) and thus will enable the first local helioseismology studies of the polar regions. Here we consider an array of science objectives to be addressed by helioseismology within the baseline telemetry allocation (51 Gbit per orbit, current baseline) and within the science observing windows (baseline 3 x 10 days per orbit). A particularly important objective is the measurement of large-scale flows at high latitudes (rotation and meridional flow), which are largely unknown but play an important role in flux transport dynamos. The full range of Earth-Sun-spacecraft angles provi...

Löptien, Björn; Gizon, Laurent; Schou, Jesper; Appourchaux, Thierry; Rodríguez, Julián Blanco; Cally, Paul S; Dominguez-Tagle, Carlos; Gandorfer, Achim; Hill, Frank; Hirzberger, Johann; Scherrer, Philip H; Solanki, Sami K

2014-01-01

145

ICESat Precision Orbit Determination  

NASA Astrophysics Data System (ADS)

Following the successful launch of the Ice, Cloud and land Elevation Satellite (ICESat) on January 13, 2003, 00:45 UTC, the GPS receiver on ICESat was turned on successfully on Jan. 17, 2003. High quality GPS data were collected since then to support Precision Orbit Determination (POD) activities. ICESat carries Geoscience Laser Altimeter System (GLAS) to measure ice-sheet topography and associated temporal changes, as well as cloud and atmospheric properties. To accomplish the ICESat science objectives, the position of the GLAS instrument in space should be determined with an accuracy of 5 cm and 20 cm in radial and horizontal components, respectively. This knowledge is acquired by the POD activities using the data collected by the GPS receiver on ICESat and the ground-based satellite laser ranging (SLR) data. It has been shown from pre-launch POD studies that the gravity model error is the dominant source of ICESat orbit errors. The predicted radial orbit errors at the ICESat orbit (600 km altitude) based on pre-launch gravity models, such as TEG-4 and EGM-96, are 7-15 cm. Performance of these gravity models and the recent gravity models from GRACE on ICESat POD were evaluated. The radial orbit accuracy is approaching 1-2 cm level with the GRACE gravity model. This paper also summarizes POD activities at Center for Space Research (CSR), which is responsible to generate ICESat POD products.

Rim, H.; Yoon, S.; Webb, C. E.; Kim, Y.; Schutz, B. E.

2003-12-01

146

DASTCOM5: A Portable and Current Database of Asteroid and Comet Orbit Solutions  

NASA Astrophysics Data System (ADS)

A portable direct-access database containing all NASA/JPL asteroid and comet orbit solutions, with the software to access it, is available for download (ftp://ssd.jpl.nasa.gov/pub/xfr/dastcom5.zip; unzip -ao dastcom5.zip). DASTCOM5 contains the latest heliocentric IAU76/J2000 ecliptic osculating orbital elements for all known asteroids and comets as determined by a least-squares best-fit to ground-based optical, spacecraft, and radar astrometric measurements. Other physical, dynamical, and covariance parameters are included when known. A total of 142 parameters per object are supported within DASTCOM5. This information is suitable for initializing high-precision numerical integrations, assessing orbit geometry, computing trajectory uncertainties, visual magnitude, and summarizing physical characteristics of the body. The DASTCOM5 distribution is updated as often as hourly to include newly discovered objects or orbit solution updates. It includes an ASCII index of objects that supports look-ups based on name, current or past designation, SPK ID, MPC packed-designations, or record number. DASTCOM5 is the database used by the NASA/JPL Horizons ephemeris system. It is a subset exported from a larger MySQL-based relational Small-Body Database ("SBDB") maintained at JPL. The DASTCOM5 distribution is intended for programmers comfortable with UNIX/LINUX/MacOSX command-line usage who need to develop stand-alone applications. The goal of the implementation is to provide small, fast, portable, and flexibly programmatic access to JPL comet and asteroid orbit solutions. The supplied software library, examples, and application programs have been verified under gfortran, Lahey, Intel, and Sun 32/64-bit Linux/UNIX FORTRAN compilers. A command-line tool ("dxlook") is provided to enable database access from shell or script environments.

Giorgini, Jon D.; Chamberlin, Alan B.

2014-11-01

147

Spiral Orbit Tribometer  

NASA Technical Reports Server (NTRS)

The spiral orbit tribometer (SOT) bridges the gap between full-scale life testing and typically unrealistic accelerated life testing of ball-bearing lubricants in conjunction with bearing ball and race materials. The SOT operates under realistic conditions and quickly produces results, thereby providing information that can guide the selection of lubricant, ball, and race materials early in a design process. The SOT is based upon a simplified, retainerless thrust bearing comprising one ball between flat races (see figure). The SOT measures lubricant consumption and degradation rates and friction coefficients in boundary lubricated rolling and pivoting contacts. The ball is pressed between the lower and upper races with a controlled force and the lower plate is rotated. The combination of load and rotation causes the ball to move in a nearly circular orbit that is, more precisely, an opening spiral. The spiral s pitch is directly related to the friction coefficient. At the end of the orbit, the ball contacts the guide plate, restoring the orbit to its original radius. The orbit is repeatable throughout the entire test. A force transducer, mounted in-line with the guide plate, measures the force between the ball and the guide plate, which directly relates to the friction coefficient. The SOT, shown in the figure, can operate in under ultra-high vacuum (10(exp -9) Torr) or in a variety of gases at atmospheric pressure. The load force can be adjusted between 45 and 450 N. By varying the load force and ball diameter, mean Hertzian stresses between 0.5 and 5.0 GPa can be obtained. The ball s orbital speed range is between 1 and 100 rpm.

Pepper, Stephen V.; Jones, William R., Jr.; Kingsbury, Edward; Jansen, Mark J.

2007-01-01

148

Congenital orbital teratoma.  

PubMed

Congenital orbital teratoma though rare is available in this environment. This is a case report of a baby with a protruding orbital mass in the left eye with all classical clinical features of teratoma. Though the histopathological report fell short of confirming the diagnosis the clinical features and outcome of management strongly suggest that the lesion is a teratoma. Multidisciplinary approach to the management not only saved the life of the baby in question but also enhanced the outcome of treatment. Good and compliant follow up for six months was experienced. Cytological test is mandatory for any suspected cases ofteratoma. PMID:20857798

Onyekwe, L O; Onwuegbuna, A N; Emejulu, J K C

2010-09-01

149

[A Roman orbital implant?].  

PubMed

During an excavation in Regensburg/Germany the skeleton of an approximately 20-year-old Roman man was found who was buried in the 3rd/4th century after Christ. A "stone" was found which fitted into the left orbit precisely. After a thorough investigation of the "stone" and with the ophthalmohistorical literature in mind an orbital "implant" as well as a petrified medical paste ("Kollyrium") could be ruled out almost with certainty. Possibly the "stone" served another medical purpose or was used for protection of the eye. PMID:23011607

Rohrbach, J M; Harbeck, M; Holzhauser, P; Tekeva-Rohrbach, C I; Mach, M; Codreanu-Windauer, S

2012-11-01

150

Orbit-orbit interaction and photonic orbital Hall effect in reflection of a light beam  

NASA Astrophysics Data System (ADS)

We examine the orbit—orbit interaction when a paraxial beam with intrinsic orbital angular momentum (IOAM) reflects at an air—glass interface. The orbital-dependent splitting of the beam intensity distribution arises due to the interaction between IOAM and extrinsic orbital angular momentum (EOAM). In addition, we find that the beam centroid shows an orbital-dependent rotation when seen along the propagation axis. However, the motion of the beam centroid related to the orbit—orbit interaction undergoes a straight line trajectory with a small angle inclining from the propagation axis. Similar to a previously developed spin-dependent splitting in the photonic spin Hall effect, the orbital-dependent splitting could lead to the photonic orbital Hall effect.

Zhang, Jin; Zhou, Xin-Xing; Ling, Xiao-Hui; Chen, Shi-Zhen; Luo, Hai-Lu; Wen, Shuang-Chun

2014-06-01

151

Sedna Orbit Animation  

NASA Technical Reports Server (NTRS)

This animation shows the location of the newly discovered planet-like object, dubbed 'Sedna,' in relation to the rest of the solar system. Starting at the inner solar system, which includes the orbits of Mercury, Venus, Earth, and Mars (all in yellow), the view pulls away through the asteroid belt and the orbits of the outer planets beyond (green). Pluto and the distant Kuiper Belt objects are seen next until finally Sedna comes into view. As the field widens the full orbit of Sedna can be seen along with its current location. Sedna is nearing its closest approach to the Sun; its 10,000 year orbit typically takes it to far greater distances. Moving past Sedna, what was previously thought to be the inner edge of the Oort cloud appears. The Oort cloud is a spherical distribution of cold, icy bodies lying at the limits of the Sun's gravitational pull. Sedna's presence suggests that this Oort cloud is much closer than scientists believed.

2004-01-01

152

Orbital Forces: Teacher Page  

NSDL National Science Digital Library

This activity demonstates orbital motions and forces using a tennis ball swung by a ribbon (this activity should be done outside). The Teacher Page contains background information, tennis ball preparation instructions, and wrap up information. This activity is part of Exploring Planets in the Classroom's Planetary Properties series.

153

Orbital Forces: Student Page  

NSDL National Science Digital Library

This activity teaches students about orbital motions and forces using a tennis ball swung by a ribbon. Students answer the question "What happens when you let the ball go?" Background information, activity procedures, and key words are provided. This activity is part of Exploring Planets in the Classroom's Planetary Properties series.

154

Interactive Molecular Orbital Diagrams  

NSDL National Science Digital Library

Here is an application for constructing the molecular orbital electron configurations of heteronuclear diatomic molecules. Energy level diagrams are given for the two different cases encountered in heteronuclear diatomics of the first short period (Li2 - Ne2). This is a useful tool for having students explore questions of bond order, magnetic properties and numbers of unpaired electrons.

155

Goddard Brouwer Orbit Bulletin  

NASA Technical Reports Server (NTRS)

The bulletin provides operational support for earth space research and technological missions by producing a tape containing pertinent spacecraft orbital information which is provided to a number of cities around the world in support of individual missions. A program description of the main and associated subroutines, and a complete description of the input, output and requirements of the bulletin program are presented.

Morgan, D. B.; Gordon, R. A.

1971-01-01

156

Magellan orbits Venus  

NASA Technical Reports Server (NTRS)

Various events surrounding Magellan's orbit of Venus are recounted. Significant events include the successful firing of a solid rocket motor while the spacecraft was behind Venus to transfer it from a solar-centered trajectory to an orbit around the planet. The spacecraft orbits Venus every 3.26 hours at a maximum altitude of 8500 km and minimum altitude of 291 km in an elliptical orbit. The successful August 16 test of the synthetic-aperture radar system is discussed, noting that it produced two strips, each about 20 km x 16,000 km, revealing details as small as 120 m. Two anomalies causing a delay in the start of mapping operations and subsequent breaks in the communication link with earth for 14.5 hours and 17.7 hours are discussed. Protective measures directed from the spacecraft's ROM during breach of contact are listed, and possible causes of the anomalies are suggested, such as solar activity or hardware or software elements, although the actual cause is not yet known.

Mclaughlin, W. I.

1990-01-01

157

Orbit Stabilization of Nanosat  

Microsoft Academic Search

An algorithm is developed to control a pulsed ÎV thruster on a small satellite to allow it to fly in formation with a host satellite undergoing time dependent atmospheric drag deceleration. The algorithm uses four short thrusts per orbit to correct for differences in the average radii of the satellites due to differences in drag and one thrust to symmetrize

DAVID J

1999-01-01

158

The Mercury Orbiter mission  

Microsoft Academic Search

A Mercury Orbiter is considered by the European Space Agency as one of the cornerstones of its Horizons 2000 programme. The scientific objectives of this mission are both planetary and magnetospheric. The spacecraft and mission concepts which resulted from the ESA assessment study and an outline of the forthcoming activities are presented.

R. Grard

1997-01-01

159

Orbits of colliding galaxies  

Microsoft Academic Search

A simple, semi-analytic method is developed for obtaining the orbits of galaxies undergoing fast collisions in which the galaxies are represented by Plummer models. The results are found to agree fairly well with those of N-body simulations.

M. Narasimha Rao; Saleh Mohamed Alladin; K. S. V. S. Narasimhan

1994-01-01

160

CO-ORBITAL OLIGARCHY  

SciTech Connect

We present a systematic examination of the changes in semimajor axis of a protoplanet as it interacts with other protoplanets in the presence of eccentricity dissipation. For parameters relevant to the oligarchic stage of planet formation, dynamical friction keeps the typical eccentricities small and prevents orbit crossing. Interactions at impact parameters greater than several Hill radii cause the protoplanets to repel each other; if the impact parameter is instead much less than the Hill radius, the protoplanets shift slightly in semimajor axis but remain otherwise unperturbed. If the orbits of two or more protoplanets are separated by less than a Hill radius, they are each pushed toward an equilibrium spacing between their neighbors and can exist as a stable co-orbital system. In the shear-dominated oligarchic phase of planet formation, we show that the feeding zones contain several oligarchs instead of only one. Growth of the protoplanets in the oligarchic phase drives the disk to an equilibrium configuration that depends on the mass ratio of protoplanets to planetesimals, {sigma}/{sigma}. Early in the oligarchic phase, when {sigma}/{sigma} is low, the spacing between rows of co-orbital oligarchs are about 5 Hill radii wide, rather than the 10 Hill radii cited in the literature. It is likely that at the end of oligarchy, the average number of co-orbital oligarchs is greater than unity. In the outer solar system, this raises the disk mass required to form the ice giants. In the inner solar system, this lowers the mass of the final oligarchs and requires more giant impacts than previously estimated. This result provides additional evidence that Mars is not an untouched leftover from the oligarchic phase, but must be composed of several oligarchs assembled through giant impacts.

Collins, Benjamin F.; Sari, Re'em [California Institute of Technology, MC 130-33, Pasadena, CA 91125 (United States)], E-mail: bfc@tapir.caltech.edu

2009-04-15

161

Precision Orbit Determination for the Lunar Reconnaissance Orbiter  

Microsoft Academic Search

The Lunar Reconnaissance Orbiter (LRO) spacecraft was launched on June 18, 2009. In mid-September 2009, the spacecraft orbit was changed from its commissioning orbit (30 x 216 km polar) to a quasi-frozen polar orbit with an average altitude of 50km (+-15km). One of the goals of the LRO mission is to develop a new lunar reference frame to facilitate future

F. G. Lemoine; E. Mazarico; D. D. Rowlands; M. H. Torrence; J. F. McGarry; G. A. Neumann; D. Mao; D. E. Smith; M. T. Zuber

2010-01-01

162

Unusual Sclerosing Orbital Pseudotumor Infiltrating Orbits and Maxillofacial Regions  

PubMed Central

Idiopathic orbital pseudotumor (IOP) is a benign inflammatory condition of the orbit without identifiable local or systemic causes. Bilateral massive orbital involvement and extraorbital extension of the IOP is very rare. We present an unusual case of IOP with bilateral massive orbital infiltration extending into maxillofacial regions and discuss its distinctive magnetic resonance imaging (MRI) features that help to exclude other entities during differential diagnoses. PMID:24991481

Toprak, Huseyin; Aralasmak, Ayse; Y?lmaz, Temel Fatih; Ozdemir, Huseyin

2014-01-01

163

Trajectory, orbit, and spectroscopic analysis of a bright fireball observed over Spain on April 13, 2013  

NASA Astrophysics Data System (ADS)

On April 13, 2013 a very bright fireball with an absolute magnitude of -13.0 ± 0.5 was recorded over the center of Spain. This sporadic event, which was witnessed by numerous casual observers throughout the whole country, was imaged from seven meteor-observing stations operated by the Spanish Meteor Network (SPMN), and its emission spectrum was also obtained in the framework of our meteor spectroscopy campaign. The atmospheric trajectory of the bolide and the heliocentric orbit of the parent meteoroid are analyzed here. The spectrum reveals a chondritic nature for this particle, which was following a Jupiter family comet orbit before its encounter with the Earth. In addition, the emission spectrum of the meteoric afterglow was recorded during about 0.8 s. The main emission lines appearing in this signal were identified and their evolution with time is also discussed. Afterglow spectra are not abundant in the literature, and these can provide important clues about the physical proceses taking place in meteoric persistent trains.

Madiedo, José M.; Trigo-Rodríguez, Josep M.; Zamorano, Jaime; Ana-Hernández, Leonor; Izquierdo, Jaime; Ortiz, José L.; Castro-Tirado, Aberto J.; Sánchez de Miguel, Alejandro; Ocaña, Francisco; Pastor, Sensi; de los Reyes, José A.; Galadí, David; de Guindos, Enrique; Organero, Faustino; Fonseca, Fernando; Cabrera-Caño, Jesús

2014-09-01

164

Close up view of the Orbiter Discovery in the Orbiter ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

Close up view of the Orbiter Discovery in the Orbiter Processing Facility at Kennedy Space Center. The view is a detail of the aft, starboard landing gear and a general view of the Thermal Protection System tiles around the landing-gear housing. - Space Transportation System, Orbiter Discovery (OV-103), Lyndon B. Johnson Space Center, 2101 NASA Parkway, Houston, Harris County, TX

165

Orbit Insertion by Mars Reconnaissance Orbiter (Artist's Concept)  

NASA Technical Reports Server (NTRS)

This is an artist's concept of NASA's Mars Reconnaissance Orbiter during the critical process of Mars orbit insertion. In order to be captured into orbit around Mars, the spacecraft must conduct a 25-minute rocket burn when it is just shy of reaching the planet. As pictured, it will pass under the red planet's southern hemisphere as it begins the insertion burn.

2005-01-01

166

Five Special Types of Orbits Around Mars  

Microsoft Academic Search

The abstract is additional with repect to the paper published in JGCD. Ordinary Earth satellites are usually placed into five categories of special orbits: sun-synchronous orbits, orbits at the critical inclination, frozen orbits, repeating ground track orbits, and geostationary orbits. This paper investigates their counterparts around Mars and examines the basic nature of these orbits, which are of special interest

Xiaodong Liu; Hexi Baoyin; Xingrui Ma

2011-01-01

167

SPECS: Orbital debris removal  

NASA Technical Reports Server (NTRS)

The debris problem has reached a stage at which the risk to satellites and spacecraft has become substantial in low Earth orbit (LEO). This research discovered that small particles posed little threat to spacecraft because shielding can effectively prevent these particles from damaging the spacecraft. The research also showed that, even though collision with a large piece of debris could destroy the spacecraft, the large pieces of debris pose little danger because they can be tracked and the spacecraft can be maneuvered away from these pieces. Additionally, there are many current designs to capture and remove large debris particles from the space environment. From this analysis, it was decided to concentrate on the removal of medium-sized orbital debris, that is, those pieces ranging from 1 cm to 50 cm in size. The current design incorporates a transfer vehicle and a netting vehicle to capture the medium-sized debris. The system is based near an operational space station located at 28.5 deg inclination and 400 km altitude. The system uses ground-based tracking to determine the location of a satellite breakup or debris cloud. These data are uploaded to the transfer vehicle, which proceeds to rendezvous with the debris at a lower altitude parking orbit. Next, the netting vehicle is deployed, tracks the targeted debris, and captures it. After expending the available nets, the netting vehicle returns to the transfer vehicle for a new netting module and continues to capture more debris in the target area. Once all the netting modules are expended, the transfer vehicle returns to the space station's orbit where it is resupplied with new netting modules from a space shuttle load. The new modules are launched by the shuttle from the ground and the expended modules are taken back to Earth for removal of the captured debris, refueling, and repacking of the nets. Once the netting modules are refurbished, they are taken back into orbit for reuse. In a typical mission, the system has the ability to capture 50 pieces of orbital debris. One mission will take approximately six months and the system is designed to allow for a 30 deg inclination change on the outgoing and incoming trips of the transfer vehicle.

1991-01-01

168

Autonomous Aerobraking for Mars Orbiters  

NASA Astrophysics Data System (ADS)

Autonomous Aerobraking is a developing technology that will reduce cost and increase flexibility of an aerobraking orbiter around Mars. Currently in its second phase of development, autonomous aerobraking could be implemented for a 2018 Mars orbiter.

Prince, J. L.

2012-06-01

169

Early History & Fiction! Orbital Motion!  

E-print Network

! (1777-1855)! �! German mathematician who contributed to many fields" �! Determination of conic section-Body Orbits are Conic Sections " #12;Orbits 102" (2-Body Problem)! �! e.g., " �! Sun and Earth or" �! Earth

Stengel, Robert F.

170

The Orbital Acceleration Research Experiment  

NASA Technical Reports Server (NTRS)

The hardware and software of NASA's proposed Orbital Acceleration Research Experiment (OARE) are described. The OARE is to provide aerodynamic acceleration measurements along the Orbiter's principal axis in the free-molecular flow-flight regime at orbital attitude and in the transition regime during reentry. Models considering the effects of electromagnetic effects, solar radiation pressure, orbiter mass attraction, gravity gradient, orbital centripetal acceleration, out-of-orbital-plane effects, orbiter angular velocity, structural noise, mass expulsion signal sources, crew motion, and bias on acceleration are examined. The experiment contains an electrostatically balanced cylindrical proofmass accelerometer sensor with three orthogonal sensing axis outputs. The components and functions of the experimental calibration system and signal processor and control subsystem are analyzed. The development of the OARE software is discussed. The experimental equipment will be enclosed in a cover assembly that will be mounted in the Orbiter close to the center of gravity.

Blanchard, R. C.; Hendrix, M. K.; Fox, J. C.; Thomas, D. J.; Nicholson, J.

1986-01-01

171

Surgical treatment of orbital cavernomas  

Microsoft Academic Search

BackgroundThere are numerous descriptions for the operative techniques applied in orbital lesions. We present a systematic overview of the surgical approaches, as determined by the location and extension of orbital cavernomas.

Uta Schick; Uwe Dott; Werner Hassler

2003-01-01

172

LRO Enters Lunar Orbit (Highlights)  

NASA Video Gallery

After a four and a half day journey from the Earth, the Lunar Reconnaissance Orbiter, or LRO, successfully entered orbit around the moon. Engineers at NASA's Goddard Space Flight Center in Greenbel...

173

Flight Paths of Orbiting Satellites  

NSDL National Science Digital Library

This is an activity to help students visualize the relationship of motion, time and space as it relates to objects orbiting the earth. They will be able to track the path of an orbiting object on a globe, plot the path of an orbiting object on a flat world map, and explain that an object orbiting earth on a plane will produce a flight path which appears as wavy lines on the earths surface.

174

Martian satellite orbits and ephemerides  

NASA Astrophysics Data System (ADS)

We discuss the general characteristics of the orbits of the Martian satellites, Phobos and Deimos. We provide a concise review of the various descriptions of the orbits by both analytical theories and direct numerical integrations of their equations of motion. After summarizing the observational data used to determine the orbits, we discuss the results of our latest orbits obtained from a least squares fit to the data.

Jacobson, R. A.; Lainey, V.

2014-11-01

175

Multidisciplinary Management of Orbital Rhabdomyosarcoma  

Microsoft Academic Search

\\u000a Rhabdomyosarcoma (RMS) is the most common orbital malignancy in childhood. Embryonal RMS and alveolar RMS are the two most\\u000a common histologic subtypes of RMS, and embryonal RMS is the most common subtype of orbital RMS. The clinical presentation\\u000a of orbital RMS depends on the tumor location in the orbit. Diagnosis is chiefly made through open biopsy, and complete initial\\u000a tumor

Winston W. Huh; Anita Mahajan

176

Orbital rhabdomyosarcomas: A review  

PubMed Central

Rhabdomyosarcoma (RMS) is a highly malignant tumor and is one of the few life-threatening diseases that present first to the ophthalmologist. It is the most common soft-tissue sarcoma of the head and neck in childhood with 10% of all cases occurring in the orbit. RMS has been reported from birth to the seventh decade, with the majority of cases presenting in early childhood. Survival has changed drastically over the years, from 30% in the 1960’s to 90% presently, with the advent of new diagnostic and therapeutic modalities. The purpose of this review is to provide a general overview of primary orbital RMS derived from a literature search of material published over the last 10 years, as well as to present two representative cases of patients that have been managed at our institute. PMID:24227982

Jurdy, Lama; Merks, Johanus H.M.; Pieters, Bradly R.; Mourits, Maarten P.; Kloos, Roel J.H.M.; Strackee, Simone D.; Saeed, Peerooz

2013-01-01

177

Tethered orbital propellant depot  

NASA Technical Reports Server (NTRS)

A planned function of the Space Station is to refurbish and refuel an advanced space-based LO2/LH2 orbit transfer vehicle. An alternative to propellant storage at the station is to use a remote facility tied to the station with a log tether. Preliminary design of such a facility is described with emphasis on fluid transfer and storage requirements. Using tether lengths of at least 300 ft, gravity gradient forces will dominate surface tension in such a system. Although gravity given transfer is difficult because of line pressure drops, fluid settling over the tank outlet greatly alleviates acquisition concerns and will facilitate vented tank fills. The major concern with a tethered orbital refueling facility is its considerable operational complexity including transport of the OTV to and from the facility.

Fester, D. A.; Rudolph, L. K.; Kiefel, E. R.

1985-01-01

178

Orbiter based construction equipment  

NASA Technical Reports Server (NTRS)

Many orbiter based activities need equipment to hold a payload steady while it is being worked on. This work may be construction, updating, repair, services, check out, or refueling operations in preparation for return to Earth. The Handling and Positioning Aid (HPA) is intended for use as general purpose equipment. The HPA provides a wide choice of work station positions, both immediately above the orbiter cargo bay and beyond. It can act in a primary docking role and, if required, can assist actively in the berthing process. From an analysis of ten reference missions, it was determined that two types of HPA mobility are needed; a tilt table, which simply swings out of the cargo bay, pivoting about an athwartships y axis, and an articulated arm. Illustration of the aid are provided.

Goodwin, C. J.

1982-01-01

179

Three orbital transfer vehicles  

NASA Technical Reports Server (NTRS)

Aerospace engineering students at the Virginia Polytechnic Institute and State University undertook three design projects under the sponsorship of the NASA/USRA Advanced Space Design Program. All three projects addressed cargo and/or crew transportation between low Earth orbit and geosynchronous Earth orbit. Project SPARC presents a preliminary design of a fully reusable, chemically powered aeroassisted vehicle for a transfer of a crew of five and a 6000 to 20000 pound payload. The ASTV project outlines a chemically powered aeroassisted configuration that uses disposable tanks and a relatively small aerobrake to realize propellant savings. The third project, LOCOST, involves a reusable, hybrid laser/chemical vehicle designed for large cargo (up to 88,200 pounds) transportation.

1990-01-01

180

Mercury orbiter transport study  

NASA Technical Reports Server (NTRS)

A data base and comparative performance analyses of alternative flight mode options for delivering a range of payload masses to Mercury orbit are provided. Launch opportunities over the period 1980-2000 are considered. Extensive data trades are developed for the ballistic flight mode option utilizing one or more swingbys of Venus. Advanced transport options studied include solar electric propulsion and solar sailing. Results show the significant performance tradeoffs among such key parameters as trip time, payload mass, propulsion system mass, orbit size, launch year sensitivity and relative cost-effectiveness. Handbook-type presentation formats, particularly in the case of ballistic mode data, provide planetary program planners with an easily used source of reference information essential in the preliminary steps of mission selection and planning.

Friedlander, A. L.; Feingold, H.

1977-01-01

181

On-orbit coldwelding  

NASA Technical Reports Server (NTRS)

Spacecraft mechanisms are required to operate in the space environment for extended periods of time. A significant concern to the spacecraft designer is the possibility of metal to metal coldwelding or significant increases in friction. Coldwelding can occur between atomically clean metal surfaces when carefully prepared in a vacuum chamber on earth. The question is whether coldwelding occurs in orbit service conditions. The results of the System Special Investigation Group's (SIG's) investigation into whether coldwelding had occurred on any Long Duration Exposure Facility (LDEF) hardware are presented. The results of a literature search into previous ground based anomalies is also presented. Results show that even though there have been no documented on-orbit coldwelding related failures, precautions should be taken to ensure that coldwelding does not occur in the space environment and that seizure does not occur in the prelaunch or launch environment.

Dursch, Harry; Spear, Steve

1991-01-01

182

Interplanetary orbit determination  

NASA Technical Reports Server (NTRS)

The logistical aspects of orbit determination (OD) in the interplanetary phase of the Mariner Mars 1971 mission are described and the working arrangements for the OD personnel, both within the Navigation Team and with outside groups are given. Various types of data used in the OD process are presented along with sources of the data. Functional descriptions of the individual elements of the OD software and brief sketches of their modes of operation are provided.

Zielenbach, J. W.; Acton, C. H.; Born, G. H.; Breckenridge, W. G.; Chao, C. C.; Duxbury, T. C.; Green, D. W.; Jerath, N.; Jordan, J. F.; Mottinger, N. A.

1973-01-01

183

Spectrophotovoltaic orbital power generation  

NASA Technical Reports Server (NTRS)

The feasibilty of a spectrophotovoltaic orbital power generation system that optically concentrates solar energy is demonstrated. A dichroic beam-splitting mirror is used to divide the solar spectrum into two wavebands. Absorption of these wavebands by GaAs and Si solar cell arrays with matched energy bandgaps increases the cell efficiency while decreasing the amount of heat that must be rejected. The projected cost per peak watt if this system is $2.50/W sub p.

Onffroy, J. R.

1980-01-01

184

'Spider' in Earth Orbit  

NASA Technical Reports Server (NTRS)

View of the Apollo 9 Lunar Module 'Spider' in a lunar landing configuration photographed by Command Module pilot David Scott inside the Command/Service Module 'Gumdrop' on the fifth day of the Apollo 9 earth-orbital mission. The landing gear on 'Spider' has been deployed. lunar surface probes (sensors) extend out from the landing gear foot pads. Inside the 'Spider' were astronauts James A. McDivitt, Apollo 9 Commander; and Russell L. Schweickart, Lunar Module pilot.

1969-01-01

185

Orbits of colliding galaxies  

Microsoft Academic Search

A simple, semi-analytic method is developed for obtaining the orbits of galaxies undergoing fast collisions in which the galaxies are represented by Plummer models. The results are found to agree fairly well with those of N-body simulations. A simple formula for obtaining the angle of deflection is deduced. The maximum angle of deflection is 180 deg for Vp\\/Vesc(p) = 1.00,

M. Narasimha Rao; Saleh Mohamed Alladin; K. S. V. S. Narasimhan

1994-01-01

186

Radiation Propulsion For Maintaining Orbits  

NASA Technical Reports Server (NTRS)

Brief report proposes radiative propulsion systems for maintaining precise orbits of spacecraft. Radiation from electrical heaters directed outward by paraboloidal reflectors to produce small forces to oppose uncontrolled drag and solar-radiative forces perturbing orbits. Minimizes or eliminates need to fire rocket thrusters to correct orbits.

Richter, Robert

1995-01-01

187

Voyager orbit determination at Jupiter  

Microsoft Academic Search

This paper summarizes the Voyager 1 and Voyager 2 orbit determination activity extending from encounter minus 60 days to the Jupiter encounter, and includes quantitative results and conclusions derived from mission experiences. The major topics covered include an identification and quantification of the major orbit determination error sources and a review of salient orbit determination results from encounter, with emphasis

J. K. Campbell; S. P. Synnott; G. J. Bierman

1983-01-01

188

Voyager orbit determination at Jupiter  

Microsoft Academic Search

This paper summarizes the Voyager 1 and Voyager 2 orbit determination activity extending from encounter minus 60 days to the Jupiter encounter, and includes quantitative results and conclusions derived from mission experience. The major topics covered include an identifica- tion and quantification of the major orbit determination error sources and a review of salient orbit determination results from encounter, with

JAMES K. CAMPBELL; STEPHEN P. SYNNOTT; GERALD J. BIERMAN

1983-01-01

189

Transverse halo orbits about Mars?  

Microsoft Academic Search

We predict a new family of charged dust rings about Mars, transverse to the ecliptic plane. These orbits are stable to the perturbations of planetary oblateness, Mars' orbital motion, and the solar wind. Lifetimes of individual orbits are limited primarily by the Lorentz force and Poynting-Robertson drag, and may exceed 1000 years. They may be populated via collisions of micrometeoroids

J. E. Howard; A. V. Krivov; F. Spahn

2003-01-01

190

Heteronuclear Diatomic Molecular Orbital Formation  

NSDL National Science Digital Library

Here is a set of movies that demonstrates heteronuclear diatomic molecular orbital formation. The orbitals start at a distance where there is little or no interatomic interaction and move to the appropriate bond distance. Orbital phase is shown by the different colors.

191

Orbiter Autoland reliability analysis  

NASA Technical Reports Server (NTRS)

The Space Shuttle Orbiter is the only space reentry vehicle in which the crew is seated upright. This position presents some physiological effects requiring countermeasures to prevent a crewmember from becoming incapacitated. This also introduces a potential need for automated vehicle landing capability. Autoland is a primary procedure that was identified as a requirement for landing following and extended duration orbiter mission. This report documents the results of the reliability analysis performed on the hardware required for an automated landing. A reliability block diagram was used to evaluate system reliability. The analysis considers the manual and automated landing modes currently available on the Orbiter. (Autoland is presently a backup system only.) Results of this study indicate a +/- 36 percent probability of successfully extending a nominal mission to 30 days. Enough variations were evaluated to verify that the reliability could be altered with missions planning and procedures. If the crew is modeled as being fully capable after 30 days, the probability of a successful manual landing is comparable to that of Autoland because much of the hardware is used for both manual and automated landing modes. The analysis indicates that the reliability for the manual mode is limited by the hardware and depends greatly on crew capability. Crew capability for a successful landing after 30 days has not been determined yet.

Welch, D. Phillip

1993-01-01

192

Ejs Keplerian Orbit Model  

NSDL National Science Digital Library

The Ejs Keplerian Orbit model displays the dynamics of a mass orbiting a much larger mass subject to Newtonian gravity. The simulation displays the motion of the smaller mass and the effective potential energy diagram. The initial energy of the system can be changed via textbox and the initial conditions can also be changed by dragging the mass or dragging the black circle in the effect potential energy diagram. You can modify this simulation if you have Ejs installed by right-clicking within the plot and selecting âOpen Ejs Modelâ from the pop-up menu item. Ejs Keplerian Orbit model was created using the Easy Java Simulations (Ejs) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_ehu_central_forces_kepler.jar file will run the program if Java is installed. Ejs is a part of the Open Source Physics Project and is designed to make it easier to access, modify, and generate computer models. Additional Ejs models for Newtonian mechanics are available. They can be found by searching ComPADRE for Open Source Physics, OSP, or Ejs.

Aguirregabiria, Juan

2008-08-18

193

Frozen Orbital Plane Solutions for Satellites in Nearly Circular Orbit  

NASA Astrophysics Data System (ADS)

This paper deals with the determination of the initial conditions (right ascension of the ascending node and inclination) that minimize the orbital plane variation for nearly circular orbits with a semimajor axis between 3 and 10 Earth radii. An analysis of two-line elements over the last 40 years for mid-, geostationary-, and high-Earth orbits has shown, for initially quasi-circular orbits, low eccentricity variations up to the geostationary altitude. This result makes the application of mathematical models based on satellite circular orbits advantageous for a fast prediction of long-term temporal evolution of the orbital plane. To this purpose, a previous model considering the combined effect due to the Earth's oblateness, moon, and sun (both in circular orbit) has been improved in terms of required computational time and accuracy. The eccentricity of the sun and moon and the equinoctial precession have been taken into account. Resonance phenomena with the lunar plane motion have been found in mid-Earth orbit. Dynamical properties concerning the precession motions of the orbital pole have been investigated, and frozen solutions for geosynchronous and navigation satellites have been proposed. Finally, an accurate model validation has also been carried out by comparing the obtained results with two-line elements of abandoned geostationary-Earth orbit and mid-Earth orbit satellites.

Ulivieri, Carlo; Circi, Christian; Ortore, Emiliano; Bunkheila, Federico; Todino, Francesco

2013-08-01

194

Voyager orbit determination at Jupiter  

NASA Technical Reports Server (NTRS)

This paper summarizes the Voyager 1 and Voyager 2 orbit determination activity extending from encounter minus 60 days to the Jupiter encounter, and includes quantitative results and conclusions derived from mission experiences. The major topics covered include an identification and quantification of the major orbit determination error sources and a review of salient orbit determination results from encounter, with emphasis on the Jupiter approach phase orbit determination. Special attention is paid to the use of combined spacecraft-based optical observations and earth-based radiometric observations to achieve accurate orbit determination during the Jupiter encounter approach phase.

Campbell, J. K.; Synnott, S. P.; Bierman, G. J.

1983-01-01

195

Orbit synthesis for target satellites  

NASA Astrophysics Data System (ADS)

The purpose of the study is to illustrate the orbit synthesis process for a hypothetical test of a direct-ascent-based kinetic energy weapon (KEW) against an instrumented test vehicle. Test arena and communications considerations for a ground-based directed energy weapon and a direct-ascent-based KEW are outlined, along with launch vehicle constraints, algorithms for off-nominal orbits, and thermal-control and orbit lifetime considerations. Focus is placed on altitude and illumination cycles, general-test and detailed-test constraints, and methodologies for assessing orbit performance. The orbit synthesis is demonstratedd, with emphasis on the test opportunity influence on orbit inclination, test window concept, selection of apogee altitude, orbit inclination, perigee altitude, launch window, and the effect of the launch date.

Wilkinson, Charles K.

196

Orbital Phase Environments and Stereoselectivities  

NASA Astrophysics Data System (ADS)

Facial selections are reviewed to propose a new theory, orbital phase environment, for stereoselectivities of organic reactions. The orbital phase environment is a generalized idea of the secondary orbital interaction between the non-reacting centers and the unsymmetrization of the orbitals at the reacting centers arising from in-phase and out-of-phase overlapping with those at the neighboring non-reacting sites. In this context, the nucleophilic addition preferentially occurs on the face of the carbonyl functionality opposite to the better electron-donating orbital at the ? position. In a similar manner to the carbonyl cases, the preferred reaction faces of olefins in electrophilic addition reactions are opposite to the better electron-donating orbitals at the ? positions. The orbital phase environments in Diels-Alder reactions are also reviewed.

Ohwada, Tomohiko

197

Orbital Debris: A Policy Perspective  

NASA Technical Reports Server (NTRS)

A viewgraph presentation describing orbital debris from a policy perspective is shown. The contents include: 1) Voyage through near-Earth Space-animation; 2) What is Orbital Debris?; 3) Orbital Debris Detectors and Damage Potential; 4) Hubble Space Telescope; 5) Mir Space Station Solar Array; 6) International Space Station; 7) Space Shuttle; 8) Satellite Explosions; 9) Satellite Collisions; 10) NASA Orbital Debris Mitigation Guidelines; 11) International Space Station Jettison Policy; 12) Controlled/Uncontrolled Satellite Reentries; 13) Return of Space Objects; 14) Orbital Debris and U.S. National Space Policy; 15) U.S Government Policy Strategy; 16) Bankruptcy of the Iridium Satellite System; 17) Inter-Agency Space Debris Coordination Committee (IADC); 18) Orbital Debris at the United Nations; 19) Chinese Anti-satellite System; 20) Future Evolution of Satellite Population; and 21) Challenge of Orbital Debris

Johnson, Nicholas L.

2007-01-01

198

Mars orbits with daily repeating ground traces  

NASA Technical Reports Server (NTRS)

This paper derives orbits at Mars with ground traces that repeat at the same times every solar day (sol). A relay orbiter in such an orbit would pass over insitu probes at the same times every sol, ensuring consistent coverage and simplifying mission design and operations. 42 orbits in five classes are characteried: 14 cicular equatorial prograde orbits; 14 circular equatorial retrograde orbits; 11 circular sun synchrounous orbits; 2 eccentroc equatorial orbits; 1 eccentric critcally inclined orbit. the paper reports on the performance of a relay orbiter in some of the orbits.

Noreen, Gary K.; Kerridge, Stuart; Diehl, Roger; neelon, Joseph; Ely, Todd; Turner, Andrew

2003-01-01

199

Orbiter door closure tools  

NASA Technical Reports Server (NTRS)

Safe reentry of the shuttle orbiter requires that the payload bay doors be closed and securely latched. Since a malfunction in the door drive or bulkhead latch systems could make safe reentry impossible, the requirement to provide tools to manually close and secure the doors was implemented. The tools would disconnect a disabled door or latch closure system and close and secure the doors if the normal system failed. The tools required to perform these tasks have evolved into a set that consists of a tubing cutter, a winch, a latching tool, and a bolt extractor. The design, fabrication, and performance tests of each tool are described.

Acres, W. R.

1980-01-01

200

Weather Satellite and Orbits  

NSDL National Science Digital Library

In this interactive, online module, students learn about satellite orbits (geostationary and polar), remote-sensing satellite instruments (radiometers and sounders), satellite images, and the math and physics behind satellite technology. The module is part of an online course for grades 7-12 in satellite meteorology, which includes 10 interactive modules. The site also includes lesson plans developed by teachers and links to related resources. Each module is designed to serve as a stand-alone lesson, however, a sequential approach is recommended. Designed to challenge students through the end of 12th grade, middle school teachers and students may choose to skim or skip a few sections.

201

Counter-Orbitals: Another Class of Co-Orbitals  

NASA Astrophysics Data System (ADS)

Co-orbital companions share the same orbital period and semi-major axis about a primary (star or planet). Heretofore there have been three recognized classes of co-orbitals: (1) Trojans librate in tadpole-shaped orbits about the equilateral Lagrange points L4 and L5, 60 degrees ahead of or behind the secondary (planet or satellite). (2) Horse-shoe companions librate about both L4 and L5, as well as the L3 Lagrange point diametrically opposite the secondary. (3) ``Quasi-satellites'' appear to be in distant retrograde orbits about the secondary, but actually are in prograde orbits about the primary with the same period as the secondary. Quasi-satellite orbits lie outside the secondary's Hill sphere, and enclose both L1 and L2, and sometimes L4 and L5 as well. In addition, some asteroids and comets are found in hybrid orbits which alternate among the above three classes, or combine some of their features. New research now reveals a fourth class of co-orbitals, which does not appear to be known before, and may be called ``counter-orbitals''. Imagine reversing the inertial velocity of a distant quasi-satellite. Then it remains in orbit about the primary, with the same period, semi-major axis, eccentricity, and orbital plane, although retrograde. But instead of remaining relatively close to the secondary, now it passes the secondary twice per orbit, near periapsis and apoapsis. The attractive impulses at these conjunctions tend to stabilize this arrangement. Numerical simulations of the general three-body problem verify that counter-orbitals can persist for over 10,000 orbits, with small vertical excursions, but a wide range of eccentricities and mass ratios. For example, Charon can maintain counter-orbital companions at least up to 3 percent of its own mass, in eccentric orbits extending from about 7050 km out to 41700 km from the center of Pluto. This may present a collision hazard to the New Horizons spacecraft.

Dobrovolskis, Anthony R.

2012-10-01

202

Visible Nulling Coronagraph Testbed Results  

NASA Technical Reports Server (NTRS)

The Extrasolar Planetary Imaging Coronagraph (EPIC) is a NASA Astrophysics Strategic Mission Concept study and a proposed NASA Discovery mission to image and characterize extrasolar giant planets in orbits with semi-major axes between 2 and 10 AU. EPIC would provide insights into the physical nature of a variety of planets in other solar systems complimenting radial velocity (RV) and astrometric planet searches. It will detect and characterize the atmospheres of planets identified by radial velocity surveys, determine orbital inclinations and masses, characterize the atmospheres around A and F stars, observed the inner spatial structure and colors of inner Spitzer selected debris disks. EPIC would be launched to heliocentric Earth trailing drift-away orbit, with a 5-year mission lifetime. The starlight suppression approach consists of a visible nulling coronagraph (VNC) that enables starlight suppression in broadband light from 480-960 nm. To demonstrate the VNC approach and advance it's technology readiness we have developed a laboratory VNC and have demonstrated white light nulling. We will discuss our ongoing VNC work and show the latest results from the VNC testbed.

Lyon, Richard G.; Clampin, Mark; Melnick, Gary; Tolls, Volker; Woodruff, Robert; Vasudevan, Gopal; Rizzo, Maxime; Thompson, Patrick

2009-01-01

203

Orbital YORP and asteroid orbit evolution, with application to Apophis  

NASA Astrophysics Data System (ADS)

Photon thrust from shape alone can produce quasi-secular changes in an asteroid's orbital elements. An asteroid in an elliptical orbit with a north-south shape asymmetry can steadily alter its elements over timescales longer than one orbital trip about the Sun. This thrust, called here orbital YORP (YORP = Yarkovsky-O'Keefe-Radzievskii-Paddack), operates even in the absence of thermal inertia, which the Yarkovsky effects require. However, unlike the Yarkovsky effects, which produce secular orbital changes over millions or billions of years, the change in an asteroid's orbital elements from orbital YORP operates only over the precession timescale of the orbit or of the asteroid's spin axis; this is generally only thousands or tens of thousands of years. Thus while the orbital YORP timescale is too short for an asteroid to secularly journey very far, it is long enough to warrant investigation with respect to 99942 Apophis, which might conceivably impact the Earth in 2036. A near-maximal orbital YORP effect is found by assuming Apophis is without thermal inertia and is shaped like a hemisphere, with its spin axis lying in the orbital plane. With these assumptions orbital YORP can change its along-track position by up to ±245 km, which is comparable to Yarkovsky effects. Though Apophis' shape, thermal properties, and spin axis orientation are currently unknown, the practical upper and lower limits are liable to be much less than the ±245 km extremes. Even so, the uncertainty in position is still likely to be much larger than the ˜0.5 km "keyhole" Apophis must pass through during its close approach in 2029 in order to strike the Earth in 2036.

Rubincam, David Parry

2007-12-01

204

Orbital construction demonstration study  

NASA Technical Reports Server (NTRS)

A conceptual design and program plan for an Orbital Construction Demonstration Article (OCDA) was developed that can be used for evaluating and establishing practical large structural assembly operations. A flight plan for initial placement and continued utility is presented as a basic for an entirely new shuttle payload line-item having great future potential benefit for space applications. The OCDA is a three-axis stabilized platform in low-earth orbit with many structural nodals for mounting large construction and fabrication equipments. This equipment would be used to explore methods for constructing the large structures for future missions. The OCDA would be supported at regular intervals by the shuttle. Construction experiments and consumables resupply are performed during shuttle visit periods. A 250 kw solar array provides sufficient power to support the shuttle while attached to the OCDA and to run construction experiments at the same time. Wide band communications with a Telemetry and Data Relay Satellite compatible high gain antenna can be used between shuttle revisits to perform remote controlled, TV assisted construction experiments.

1976-01-01

205

The orbital surgeon.  

PubMed Central

While the number of orbital surgeons is limited, it is hoped these can be recognized and patients referred to them by ophthalmologists not interested or trained in that specialty. Let the orbital surgeon determine whether he can handle the problem in 1 to 2 days, or whether a neurosurgeon should do the procedure or make it a joint effort. It may well involve other specialty team effort approaches. It is essential to have an understanding of x-rays, CT, angiography, and MRI techniques and films. Sit with these specialists to learn more and help to avoid negative, misdiagnosis reports in the interest of the patient. Use judgement in helping the patient decide on ophthalmic or the more extensive neurosurgical approach after careful study and what is in their best interest. The team approach is used in well established medical centers with the ophthalmologist and neurosurgeon (or other specialist) working together in the best interest of the patient. This is more interesting and keeps the ophthalmologist in the mainstream of medicine. Images FIGURE 1 A FIGURE 1 B FIGURE 1 C FIGURE 2 FIGURE 3 A FIGURE 3 B FIGURE 3 C FIGURE 3 D FIGURE 4 A FIGURE 4 B FIGURE 5 A FIGURE 5 B FIGURE 6 A FIGURE 6 B FIGURE 7 A FIGURE 7 B FIGURE 7 C FIGURE 8 A FIGURE 8 B FIGURE 9 PMID:2979017

Kennedy, R E

1988-01-01

206

General view of the Orbiter Discovery in the Orbiter Processing ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

General view of the Orbiter Discovery in the Orbiter Processing Facility at Kennedy Space Center showing the payload bay doors open exposing the heat-dissipating radiator panels located on the inside of the payload bay doors. Also in the view is the boom portion of the boom sensor system deployed as part of the return to flight procedures after STS-107 to inspect the orbiter's thermal protection system. The Remote Manipulator System, the "Canadarm", and the airlock are seen in the background of the image. - Space Transportation System, Orbiter Discovery (OV-103), Lyndon B. Johnson Space Center, 2101 NASA Parkway, Houston, Harris County, TX

207

Orbital Structure and Asymptotic Orbits in Barred-Spiral Galaxies  

NASA Astrophysics Data System (ADS)

Using frequency analysis we find the orbital structure of a self-consistent N-body configuration simulating a rotating barred-spiral galaxy. We detect the main families of the regular orbits and of the chaotic ones, separately. Chaotic orbits play a major role in supporting the outer envelope of the bar as well as the ring and the spiral arms. The explanation is given by studying the unstable asymptotic curves of the main unstable periodic orbits of the system. A new type of stickiness phenomenon near the main unstable asymptotic curves on the phase space seems to be responsible for the galaxy’s shape outside corotation.

Harsoula, M.; Kalapotharakos, C.; Contopoulos, G.

2010-07-01

208

Orbit selection for a Mars geoscience/climatology orbiter  

NASA Technical Reports Server (NTRS)

This paper is a presentation of recent work to provide orbit design and selection criteria for a close, nearly polar, nearly circular orbit of Mars. The main aspects of the work are the evaluation of atmospheric drag for altitude selection, the orbit evolution for variations in periapsis altitude, and the interactions of those factors with the science objectives of the MGCO mission. A dynamic model of the Mars atmosphere is available from parallel efforts and the latest estimates of the upper atmospheric density and its time history are incorporated into the analysis to provide a final orbit that satisfies planetary quarantine requirements.

Uphoff, C.

1984-01-01

209

Photometry of 2006 RH{120}: an asteroid temporary captured into a geocentric orbit  

NASA Astrophysics Data System (ADS)

Aims: From July 2006 to July 2007 a very small asteroid orbited the Earth within its Hill sphere. We used this opportunity to study its rotation and estimate its diameter and shape. Methods: Due to its faintness, 2006 RH{120} was observed photometrically with the new 10-m SALT telescope at the SAAO (South Africa). We obtained data on four nights: 11, 15, 16, and 17 March 2007 when the solar phase angle remained almost constant at 74°. The observations lasted about an hour each night and the object was exposed for 7-10 s through the “clear” filter. Results: From the lightcurves obtained on three nights we derived two solutions for a synodical period of rotation: P1 = 1.375 ± 0.001 min and P2 = 2.750 ± 0.002 min. The available data are not sufficient to choose between them. The absolute magnitude of the object was found to be H = 29.9 ± 0.3 mag (with the assumed slope parameter G = 0.25) and its effective diameter D = 2-7 m, depending on the geometric albedo pV (with the most typical near-Earth asteroids albedo pV = 0.18 its diameter would be D = 3.3 ± 0.4 m). The body has an elongated shape with the a/b ratio greater than 1.4. It probably originates in low-eccentricity Amor or Apollo orbits. There is still a possibility, which needs further investigation, that it is a typical near-Earth asteroid that survived the aerobraking in the Earth's atmosphere and returned to a heliocentric orbit similar to that of the Earth. Based on observations made with the Southern African Large Telescope (SALT).

Kwiatkowski, T.; Kryszczy?ska, A.; Poli?ska, M.; Buckley, D. A. H.; O'Donoghue, D.; Charles, P. A.; Crause, L.; Crawford, S.; Hashimoto, Y.; Kniazev, A.; Loaring, N.; Romero Colmenero, E.; Sefako, R.; Still, M.; Vaisanen, P.

2009-03-01

210

Mars Observer orbit determination analysis  

NASA Technical Reports Server (NTRS)

Results are presented of a simulated orbit determination analysis for three phases of the Mars Observer mission (interplanetary cruise, orbit insertion, and mapping), together with a summary of orbital accuracies throughout the Mars Observer mission. The plan for achieving the navigation objectives of the Mars Observer mission is described. These objectives are to navigate the Mars Observer spacecraft to Mars and achieve accurate targeting at Mars; to propulsively maneuver the spacecraft into a 3-day period, capture orbit; to navigate the spacecraft into a 1.96-hr period low-altitude, nearly circular mapping orbit; and to maintain Mars Observer in the mapping orbit throughout the 687 days devoted for scientific data acquisition. Factors that will affect the spacecraft during each of the three phases are discussed.

Esposito, Pasquale; Roth, Duane; Demcak, Stuart

1991-01-01

211

Mars Observer orbit determination analysis  

NASA Astrophysics Data System (ADS)

Results are presented of a simulated orbit determination analysis for three phases of the Mars Observer mission (interplanetary cruise, orbit insertion, and mapping), together with a summary of orbital accuracies throughout the Mars Observer mission. The plan for achieving the navigation objectives of the Mars Observer mission is described. These objectives are to navigate the Mars Observer spacecraft to Mars and achieve accurate targeting at Mars; to propulsively maneuver the spacecraft into a 3-day period, capture orbit; to navigate the spacecraft into a 1.96-hr period low-altitude, nearly circular mapping orbit; and to maintain Mars Observer in the mapping orbit throughout the 687 days devoted for scientific data acquisition. Factors that will affect the spacecraft during each of the three phases are discussed.

Esposito, Pasquale; Roth, Duane; Demcak, Stuart

1991-10-01

212

Geostationary Earth Orbit Satellite Model  

NSDL National Science Digital Library

The Geostationary Earth Orbit Satellite Model is a simple angular velocity model that uses Java3D for a realistic visualization of satellites in geostationary orbits. Students can view and explore the behavior of geostationary orbits, non-geostationary orbits, and non-physical orbits. This model tests the Java 3D implementation of the EJS 3D library. A warning message will appear if the Java 3D library is not available. The Geostationary Earth Orbit Satellite Model was developed using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the jar file will run the program if Java is installed. You can modify this simulation if you have EJS installed by right-clicking within the map and selecting "Open Ejs Model" from the pop-up menu item.

Wee, Loo K.

2012-04-08

213

Orbital myositis: Diagnosis and management  

Microsoft Academic Search

Orbital myositis is an inflammatory process that primarily involves the extraocular muscles and most commonly affects young\\u000a adults in the third decade of life, with a female predilection. Clinical characteristics of orbital myositis include orbital\\u000a and periorbital pain, ocular movement impairment, diplopia, proptosis, swollen eyelids, and conjunctival hyperemia. The most\\u000a common presentation is acute and unilateral, which initially responds to

Roberta M. S. Costa; Oana M. Dumitrascu; Lynn K. Gordon

2009-01-01

214

Orbit synthesis for target satellites  

Microsoft Academic Search

The purpose of the study is to illustrate the orbit synthesis process for a hypothetical test of a direct-ascent-based kinetic energy weapon (KEW) against an instrumented test vehicle. Test arena and communications considerations for a ground-based directed energy weapon and a direct-ascent-based KEW are outlined, along with launch vehicle constraints, algorithms for off-nominal orbits, and thermal-control and orbit lifetime considerations.

Charles K. Wilkinson

1990-01-01

215

Ancient schwannoma of the orbit.  

PubMed

Schwannoma, also referred to as neurilemmoma or peripheral neurinoma, is an unusual orbital benign tumour that may pose diagnostic challenges. Awareness of the clinical features that may be associated with the tumour and prompt surgical excision with histopathologic examination enable correct diagnosis. The authors describe a progressively increasing inferolateral orbital mass in a 32-year-old patient that was demonstrated to be an orbital ancient schwannoma. PMID:23316621

Pecorella, I; Toth, J; Lukats, O

2012-08-01

216

Aerobraked orbital transfer vehicle definition  

NASA Technical Reports Server (NTRS)

A new technique has been developed to enhance the use of upper atmosphere aerobraking for increased performance from orbital transfer vehicles. This technique utilizes a pressure supported drag brake and the orbital transfer vehicle main engine to modulate aerodynamic drag and also to alleviate the aerodynamic heating during a grazing pass through the atmosphere. Performance analyses of vehicles utilizing all-propulsive or aerobraking during round trip missions from low earth orbit (LEO) to geo-synchronous earth orbit (GEO) and back shows that aerobraking allows a given vehicle to deliver approximately twice as much payload to GEO and return. Aerobraking also provides more than twice the round trip payload.

Andrews, D. G.; Bloetscher, F.

1981-01-01

217

Nongravitational motions of comets: component of the recoil force normal to orbital plane  

NASA Astrophysics Data System (ADS)

The significance and detectability of a normal component of the nongravitational acceleration that perturbs the motions of periodic comets are examined by comparing the total perturbation effect, calculated from the component's empirical term in the equations of motion integrated over the orbital period, with the cumulative perturbations of the longitude of the ascending node and the orbital inclination brought about by the momentum that is transferred to the nucleus due to water outgassing from discrete active regions. It is shown that the approximation of temporal variations in the recoil acceleration computed using the well-known g(r) law, which is symmetrical with respect to perihelion, implies that the cumulative nongravitational perturbations of the two orbital elements are accounted for in a fashion that is inconsistent with the perturbation theory. The net result is that, in general, the value of the Style II nongravitational parameter that is consistent with the cumulative effect on the inclination, iA3, differs from the parameter's expected value that describes the cumulative effect on the nodal line, ?A3. The parameter's distributions as functions of the spin vector and the direction of the ejecta's vector (described by the thrust angle) are represented graphically for several heliocentric orbits. Symmetries with respect to particular values of the argument of perihelion, the rotation constants, and the thrust angle that apply in the case of a baseline model (which involves assumptions of a single source and the absence of sublimation lags) are identified. The magnitudes of the parameter A3 derived from orbit- determination runs are found to be generally compatible with the presented interpretation in that they are not excessive, thus supporting the evidence presented in an earlier paper (Sekanina 1993) and based upon information on the transverse and radial components of the recoil force. The values of iA3 and ?A3 are shown to coincide for certain spin-axis orientations and it is only then that the parameter A3 should reliably be determined from an orbital solution that employs the standard g(r) law. One such scenario appears to be closely approximated by Periodic Comet Clark, for which the data available are shown to provide meaningful constraints on the bulk properties of its nucleus. A potential need for a revision of the non-gravitational terms in the equations of motion is suggested.

Sekanina, Z.

1993-09-01

218

Skylab Orbiter Workshop Illustration  

NASA Technical Reports Server (NTRS)

This cutaway illustration shows the characteristics and basic elements of the Skylab Orbiter Workshop (OWS). The OWS was divided into two major compartments. The lower level provided crew accommodations for sleeping, food preparation and consumption, hygiene, waste processing and disposal, and performance of certain experiments. The upper level consisted of a large work area and housed water storage tanks, a food freezer, storage vaults for film, scientific airlocks, mobility and stability experiment equipment, and other experimental equipment. The compartment below the crew quarters was a container for liquid and solid waste and trash accumulated throughout the mission. A solar array, consisting of two wings covered on one side with solar cells, was mounted outside the workshop to generate electrical power to augment the power generated by another solar array mounted on the solar observatory. Thrusters were provided at one end of the workshop for short-term control of the attitude of the space station.

1972-01-01

219

Orbiting Carbon Observatory  

NASA Technical Reports Server (NTRS)

Human impact on the environment has produced measurable changes in the geological record since the late 1700s. Anthropogenic emissions of CO2 today may cause the global climate to depart for its natural behavior for many millenia. CO2 is the primary anthropogenic driver of climate change. The Orbiting Carbon Observatory goals are to help collect measurements of atmospheric CO2, answering questions such as why the atmospheric CO2 buildup varies annually, the roles of the oceans and land ecosystems in absorbing CO2, the roles of North American and Eurasian sinks and how these carbon sinks respond to climate change. The present carbon cycle, CO2 variability, and climate uncertainties due atmospheric CO2 uncertainties are highlighted in this presentation.

Miller, Charles E.

2005-01-01

220

Orbital science's 'Bermuda Triangle'  

NASA Astrophysics Data System (ADS)

The effects of a part of the inner Van Allen belt lying closest to the earth, known as the South Atlantic Anomaly (SAA) upon spacecraft including the Hubble Space Telescope (HST), are discussed. The area consists of positively charged ions and electrons from the Van Allen Belt which become trapped in the earth's dipole field. Contor maps representing the number of protons per square centimeter per second having energies greater than 10 million electron volts are presented. It is noted that the HST orbit causes it to spend about 15 percent of its time in the SAA, but that, unlike the experience with earlier spacecraft, the satellite's skin, internal structure, and normal electronic's packaging provides sufficient protection against eletrons, although some higher energy protons still get through. Various charged particle effects which can arise within scientific instruments including fluorescence, Cerenkov radiation, and induced radioactivity are described.

Sherrill, Thomas J.

1991-02-01

221

TOPEX orbital radiation study  

NASA Technical Reports Server (NTRS)

The space radiation environment of the TOPEX spacecraft is investigated. A single trajectory was considered. The external (surface incident) charged particle radiation, predicted for the satellite, is determined by orbital flux integration for the specified trajectory. The latest standard models of the environment are used in the calculations. The evaluation is performed for solar maximum conditions. The spacecraft exposure to cosmic rays of galactic origin is evaluated over its flight path through the magnetosphere in terms of geomagnetic shielding effects, both for surface incident heavy ions and for particles emerging behind different material thickness. Limited shielding and dose evaluations are performed for simple infinite slab and spherical geometries. Results, given in graphical and tabular form, are analyzed, explained, and discussed. Conclusions are presented and commented on.

Stassinopoulos, E. G.; Barth, J. M.

1984-01-01

222

Orbital magnetic ratchet effect  

NASA Astrophysics Data System (ADS)

Magnetic ratchets—two-dimensional systems with superimposed noncentrosymmetric ferromagnetic gratings—are considered theoretically. It is demonstrated that excitation by radiation results in a directed motion of two-dimensional carriers due to the pure orbital effect of the periodic magnetic field. Magnetic ratchets based on various two-dimensional systems such as topological insulators, graphene, and semiconductor heterostructures are investigated. The mechanisms of the electric current generation caused by both radiation-induced heating of carriers and by acceleration in the radiation electric field in the presence of a space-oscillating Lorentz force are studied in detail. The electric currents sensitive to the linear polarization plane orientation as well as to the radiation helicity are calculated. It is demonstrated that the frequency dependence of the magnetic ratchet currents is determined by the dominant elastic-scattering mechanism of two-dimensional carriers and differs for the systems with linear and parabolic energy dispersions.

Budkin, G. V.; Golub, L. E.

2014-09-01

223

Geology orbiter comparison study  

NASA Technical Reports Server (NTRS)

Instrument requirements of planetary geology orbiters were examined with the objective of determining the feasibility of applying standard instrument designs to a host of terrestrial targets. Within the basic discipline area of geochemistry, gamma-ray, X-ray fluorescence, and atomic spectroscopy remote sensing techniques were considered. Within the discipline area of geophysics, the complementary techniques of gravimetry and radar were studied. Experiments using these techniques were analyzed for comparison at the Moon, Mercury, Mars and the Galilean satellites. On the basis of these comparative assessments, the adaptability of each sensing technique was judged as a basic technique for many targets, as a single instrument applied to many targets, as a single instrument used in different mission modes, and as an instrument capability for nongeoscience objectives.

Cutts, J. A. J.; Blasius, K. R.; Davis, D. R.; Pang, K. D.; Shreve, D. C.

1977-01-01

224

Hypervelocity orbital intercept guidance  

NASA Astrophysics Data System (ADS)

Terminal guidance of a hypervelocity exo-atmospheric orbital interceptor with free end-time is examined. The pursuer is constrained to lateral thrusting with the evader modeled as an ICBM in its final boost phase. Proportional navigation, optimal control using certainty equivalence, dual control, and control with optimum thrust spacing are all examined. Also, a new approach called certainty control is developed for this problem. This algorithm constrains the final state to a function of projected estimate error to reduce control energy expenditure. All methods model the trajectories using splines and employ eight state Extended Kalman Filters with line-of-sight and range updates. The relative effectiveness of these control strategies is illustrated by applying them to various intercept problems.

Alfano, Salvatore

1988-04-01

225

Exploratory orbit analysis  

SciTech Connect

Unlike the other documents in these proceedings, this paper is neither a scientific nor a technical report. It is, rather, a short personal essay which attempts to describe an Exploratory Orbit Analysis (EOA) environment. Analyzing the behavior of a four or six dimensional nonlinear dynamical system is at least as difficult as analyzing events in high-energy collisions; the consequences of doing it badly, or slowly, would be at least as devastating; and yet the level of effort and expenditure invested in the latter, the very attention paid to it by physicists at large, must be two orders of magnitude greater than that given to the former. It is difficult to choose the model which best explains the behavior of a physical device if one does not first understand the behavior of the available models. The time is ripe for the development of a functioning EOA environment, which I will try to describe in this paper to help us achieve this goal.

Michelotti, L.

1989-03-01

226

Evolution of asteroid orbits that are orbitally commensurable with Mars  

Microsoft Academic Search

The statistical properties of the distribution of asteroids that have first-order orbital commensurability with Mars are qualitatively interpreted within the framework of the exterior version of the circular restricted three-body problem. Numerical parameters are derived for the orbital evolution of some resonant asteroids.

I. A. Gerasimov; B. R. Mushailov

1992-01-01

227

Optimal transfers from an Earth orbit to a Mars orbit  

Microsoft Academic Search

This paper deals with the optimal transfer of a spacecraft from a low Earth orbit (LEO) to a low Mars orbit (LMO). The transfer problem is formulated via a restricted four-body model in that the spacecraft is considered subject to the gravitational fields of Earth, Mars, and Sun along the entire trajectory. This is done to achieve increased accuracy with

A. Miele; T. Wang

1999-01-01

228

Orbiter-orbiter and orbiter-lander tracking using same-beam interferometry  

NASA Technical Reports Server (NTRS)

Two spacecraft orbiting Mars will subtend a small angle as viewed from Earth. This angle will usually be smaller than the beam width of a single radio antenna. Thus the two spacecraft may be tracked simultaneously by a single Earth-based antenna. The same-beam interferometry (SBI) technique involves using two widely separated antennas, each observing the two spacecraft, to produce a measurement of the angular separation of the two spacecraft in the plane of the sky. The information content of SBI data is thus complementary to the line-of-sight information provided by conventional Doppler data. The inclusion of SBI data with the Doppler data in a joint orbit estimation procedure can desensitize the solution to gravity mismodeling and result in improved orbit determination accuracy. This article presents an overview of the SBI technique, a measurement error analysis, and an error covariance analysis of some examples of the application of SBI to orbit determination. For hypothetical scenarios involving the Mars Observer and the Russian Mars '94 spacecraft, orbit determination accuracy improvements of up to an order of magnitude are predicted, relative to the accuracy that can be obtained by using only Doppler data acquired separately from each spacecraft. Relative tracking between a Mars orbiter and a lander fixed on the surface of Mars is also studied. Results indicate that the lander location may be determined to a few meters, while the orbiter ephemeris may be determined with accuracy similar to the orbiter-orbiter case.

Folkner, William M.; Border, J. S.

1992-01-01

229

Artificial frozen orbits around Mercury  

NASA Astrophysics Data System (ADS)

Orbits around Mercury are influenced by the strong elliptic third-body perturbation, especially for high eccentricity orbits, the periapsis altitude changes dramatically. Frozen orbits whose mean eccentricity and argument of perigee remain constants are obviously a good choice for space missions, but the forming conditions are too harsh to meet practical needs. To deal with this problem, a continuous control method that combines analytical theory and parameter optimization is proposed to build an artificial frozen orbit. The artificial frozen orbits are investigated on the basis of double averaged Hamiltonian, of which the second and third zonal harmonics and the perturbation of elliptic third-body gravity are considered. In this paper, coefficients of perturbations which satisfy the conditions of frozen orbits are involved as control parameters, and the relevant artificial perturbations are compensated by the control strategy. So probes around Mercury can be kept on frozen orbit under the influence of continuous control force. Then complex method of optimization is used to search for the energy optimized artificial frozen orbits. The choosing of optimal parameters, the objective function setting and other issues are also discussed in the study. Evolution of optimal control parameters are given in large ranges of semi-major axis and eccentricity, through the variation of these curves, the fuel efficiency is discussed. The result shows that the control method proposed in this paper can effectively maintain the eccentricity and argument of perigee frozen.

Ma, Xue; Li, Junfeng

2013-12-01

230

Constraint Orbital Branching JAMES OSTROWSKI  

E-print Network

Constraint Orbital Branching JAMES OSTROWSKI Department of Industrial and Systems Engineering@di.univaq.it · smriglio@di.univaq.it November 15, 2007 Abstract Orbital branching is a method for branching on variables in integer programming that reduces the likelihood of evaluating redundant, isomorphic nodes in the branch

Linderoth, Jeffrey T.

231

Newton's hypothetical orbits independently derived.  

NASA Astrophysics Data System (ADS)

The mathematical results of four hypothetical orbital problems from the Principia are confirmed by an independent physical method. Each orbital problem that Newton posed and solved is characterized as follows. Given the shape of the orbit and the position of the force center, find the functional form of the central attractive force that will keep a body moving around the orbit. None of Newton's hypothetical orbital problems has so far found any apparent practical application, whereas the Kepler problem, also solved by Newton in the Principia, is of great importance to physics. The Kepler problem too can be derived easily by the present method. Newton used primarily geometrical constructions and logical deductions to arrive at his force functions. In contrast to this, the present (inverse) approach is based on a force balance: as a body moves along a curved path the outward centrifugal force always balances the component of the inward attractive force that is perpendicular to the orbit. Taking the functional form for the central force derived by Newton and inserting it into the force balance, the orbital shape can be derived by solving an ordinary second-order differential equation-the forced harmonic oscillator equation. Two of Newton's four force functions examined in this way lead to (different) fully nonlinear differential equations, which, surprisingly, can both be solved analytically and in closed form by means of the elementary functions that describe the shapes of the orbits.

Kenyon, K. E.

232

Orbital evolution around irregular bodies  

Microsoft Academic Search

The new profiles of the space missions aimed at asteroids and comets, moving from fly-bys to rendezvous and orbiting, call for new spaceflight dynamics tools capable of propagating orbits in an accurate way around these small irregular objects. Moreover, interesting celestial mechanics and planetary science problems, requiring the same sophisticated tools, have been raised by the first images of asteroids

A. Rossi; F. Marzari; P. Farinella

1999-01-01

233

What is a MISR orbit?  

... during one half of the complete orbit or a bit less. Of course, the Earth itself keeps turning around its own axis while Terra proceeds ... to 9 days (Equator), depending on its latitude, but of course under a variety of angular conditions. An Orbit/Date Conversion ...

2013-03-05

234

Chelyabinsk Superbolide: a detailed analysis of the passage through the~atmosphere and orbit determination  

NASA Astrophysics Data System (ADS)

A detailed analysis of the passage through the atmosphere of a very bright meteor that exploded in the air near Chelyabinsk, Russia on February 15, 2013 is presented. A number of videos and photographs were examined thoroughly to determine the meteor trajectory beginning from the recorded atmospheric entry height of about 62.5 km until its disappearance at about 9.8 km. The calculated velocity changes as a function time revealed an unusual behavior: during the first 10 seconds the meteor velocity increased from 16.6 km/s up to about 20.6 km/s in the main air burst at the altitude of 26.5 km. Afterwards it decreased rapidly. The light curves derived from videos enabled the total radiant energy and mass loss variations to be calculated. The heliocentric orbit of the meteoroid and possible parent bodies were computed. We proposed an additional 'close approaches' method to the existing method of checking meteoroid/bolide parent bodies based on different D-criteria.

W?odarczyk, K.; W?odarczyk, I.

2014-07-01

235

Precision Orbit Determination for the Lunar Reconnaissance Orbiter  

NASA Astrophysics Data System (ADS)

The Lunar Reconnaissance Orbiter (LRO) spacecraft was launched on June 18, 2009. In mid-September 2009, the spacecraft orbit was changed from its commissioning orbit (30 x 216 km polar) to a quasi-frozen polar orbit with an average altitude of 50km (+-15km). One of the goals of the LRO mission is to develop a new lunar reference frame to facilitate future exploration. Precision Orbit Determination is used to achieve the accuracy requirements, and to precisely geolocate the high-resolution datasets obtained by the LRO instruments. In addition to the tracking data most commonly used to determine spacecraft orbits in planetary missions (radiometric Range and Doppler), LRO benefits from two other types of orbital constraints, both enabled by the Lunar Orbiter Laser Altimeter (LOLA) instrument. The altimetric data collected as the instrument's primary purpose can be used to derive constraints on the orbit geometry at the times of laser groundtrack intersections (crossovers). The multi-beam configuration and high firing-rate of LOLA further improves the strength of these crossovers, compared to what was possible with the MOLA instrument onboard Mars Global Surveyor (MGS). Furthermore, one-way laser ranges (LR) between Earth International Laser Ranging Service (ILRS) stations and the spacecraft are made possible by the addition of a small telescope mounted on the spacecraft high-gain antenna. The photons received from Earth are transmitted to one LOLA detector by a fiber optics bundle. Thanks to the accuracy of the LOLA timing system, the precision of 5-s LR normal points is below 10cm. We present the first results of the Precision Orbit Determination (POD) of LRO through the commissioning and nominal phases of the mission. Orbit quality is discussed, and various gravity fields are evaluated with the new (independent) LRO radio tracking data. The altimetric crossovers are used as an independent data type to evaluate the quality of the orbits. The contribution of the LR data is assessed. Multi-arc solutions over entire months are presented, which allow to strengthen the LR data because fewer clock-related parameters need to be adjusted. Finally, a preliminary 1-month solution with altimetric crossover constraints is evaluated and discussed

Lemoine, F. G.; Mazarico, E.; Rowlands, D. D.; Torrence, M. H.; McGarry, J. F.; Neumann, G. A.; Mao, D.; Smith, D. E.; Zuber, M. T.

2010-05-01

236

VSOP-2 Orbit Determination  

NASA Astrophysics Data System (ADS)

Precise orbit determination (POD) is a key factor to enable phase referencing observations with Astro-G. A POD accuracy of 30 cm is required for efficient X-band phase referencing observations, accuracy of 6 cm for K-band observations, and accuracy of 3 cm for Q-band observations. For the POD, Astro-G will be equipped with a GPS/Galileo receiver and a SLR (Satellite Laser Ranging) retroreflector array. Four POD antennas will be equipped on four sides of the satellite body, to cover all directions. The SLR will be used as a complement to the GPS at middle-to-high altitude. Because the refroreflector array should always face to the Earth direction, it will be set up on the Ka-link antenna gimbal. The most significant perturbing force for the Astro-G is solar radiation pressure (SRP). The reflectivity of each surface component should be preliminary measured in detail to model the SRP. The estimated achievable POD accuracy at apogee is 10 ˜ 30 cm in nominal case. Phase referencing observations in K- or Q-band can be performed if the enough amount of SLR tracking data can be obtained at high altitudes.

Takeuchi, H.; VSOP-2 Orbit Determination Sub-Working Group

2009-08-01

237

Orbiter Camera Payload System  

NASA Technical Reports Server (NTRS)

Components for an orbiting camera payload system (OCPS) include the large format camera (LFC), a gas supply assembly, and ground test, handling, and calibration hardware. The LFC, a high resolution large format photogrammetric camera for use in the cargo bay of the space transport system, is also adaptable to use on an RB-57 aircraft or on a free flyer satellite. Carrying 4000 feet of film, the LFC is usable over the visible to near IR, at V/h rates of from 11 to 41 milliradians per second, overlap of 10, 60, 70 or 80 percent and exposure times of from 4 to 32 milliseconds. With a 12 inch focal length it produces a 9 by 18 inch format (long dimension in line of flight) with full format low contrast resolution of 88 lines per millimeter (AWAR), full format distortion of less than 14 microns and a complement of 45 Reseau marks and 12 fiducial marks. Weight of the OCPS as supplied, fully loaded is 944 pounds and power dissipation is 273 watts average when in operation, 95 watts in standby. The LFC contains an internal exposure sensor, or will respond to external command. It is able to photograph starfields for inflight calibration upon command.

1980-01-01

238

Radiation therapy for orbital lymphoma  

SciTech Connect

Purpose: To describe radiation techniques and evaluate outcomes for orbital lymphoma. Methods and Materials: Forty-six patients (and 62 eyes) with orbital lymphoma treated with radiotherapy between 1987 and 2003 were included. The majority had mucosa-associated lymphoid tissue (48%) or follicular (30%) lymphoma. Seventeen patients had prior lymphoma at other sites, and 29 had primary orbital lymphoma. Median follow-up was 46 months. Results: The median dose was 30.6 Gy; one-third received <30 Gy. Electrons were used in 9 eyes with disease confined to the conjunctiva or eyelid, and photons in 53 eyes with involvement of intraorbital tissues to cover entire orbit. Local control rate was 98% for all patients and 100% for those with indolent lymphoma. Three of the 26 patients with localized primary lymphoma failed distantly, resulting in a 5-year freedom-from-distant-relapse rate of 89%. The 5-year disease-specific and overall survival rates were 95% and 88%, respectively. Late toxicity was mainly cataract formation in patients who received radiation without lens block. Conclusions A dose of 30 Gy is sufficient for indolent orbital lymphoma. Distant relapse rate in patients with localized orbital lymphoma was lower than that reported for low-grade lymphoma presenting in other sites. Orbital radiotherapy can be used for salvage of recurrent indolent lymphoma.

Zhou Ping [Department of Radiation Oncology, Brigham and Women's Hospital and Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA (United States)]. E-mail: pzhou@partners.org; Ng, Andrea K. [Department of Radiation Oncology, Brigham and Women's Hospital and Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA (United States); Silver, Barbara [Department of Radiation Oncology, Brigham and Women's Hospital and Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA (United States); Li Sigui [Department of Biostatistical Sciences, Dana-Farber Cancer Institute, Boston, MA (United States); Hua Ling [Department of Radiation Oncology, Brigham and Women's Hospital and Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA (United States); Mauch, Peter M. [Department of Radiation Oncology, Brigham and Women's Hospital and Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA (United States)

2005-11-01

239

Geostationary orbit determination using SATRE  

NASA Astrophysics Data System (ADS)

A new strategy of precise orbit determination (POD) for GEO (Geostationary Earth Orbit) satellite using SATRE (SAtellite Time and Ranging Equipment) is presented. Two observation modes are proposed and different channels of the same instruments are used to construct different observation modes, one mode receiving time signals from their own station and the other mode receiving time signals from each other for two stations called pairs of combined observations. Using data from such a tracking network in China, the results for both modes are compared. The precise orbit determination for the Sino-1 satellite using the data from 6 June 2005 to 13 June 2005 has been carried out in this work. The RMS (Root-Mean-Square) of observing residuals for 3-day solutions with the former mode is better than 9.1 cm. The RMS of observing residuals for 3-day solutions with the latter mode is better than 4.8 cm, much better than the former mode. Orbital overlapping (3-day orbit solution with 1-day orbit overlap) tests show that the RMS of the orbit difference for the former mode is 0.16 m in the radial direction, 0.53 m in the along-track direction, 0.97 m in the cross-track direction and 1.12 m in the 3-dimension position and the RMS of the orbit difference for the latter mode is 0.36 m in the radial direction, 0.89 m in the along-track direction, 1.18 m in the cross-track direction and 1.52 m in the 3-dimension position, almost the same as the former mode. All the experiments indicate that a meter-level accuracy of orbit determination for geostationary satellite is achievable.

Lei, Hui; Li, ZhiGang; Yang, XuHai; Wu, WenJun; Cheng, Xuan; Yang, Ying; Feng, ChuGang

2011-09-01

240

Extrasolar Planet Orbits and Eccentricities  

E-print Network

The known extrasolar planets exhibit many interesting and surprising features--extremely short-period orbits, high-eccentricity orbits, mean-motion and secular resonances, etc.--and have dramatically expanded our appreciation of the diversity of possible planetary systems. In this review we summarize the orbital properties of extrasolar planets. One of the most remarkable features of extrasolar planets is their high eccentricities, far larger than seen in the solar system. We review theoretical explanations for large eccentricities and point out the successes and shortcomings of existing theories.

Scott Tremaine; Nadia L. Zakamska

2003-12-01

241

[Materials used in orbital surgery].  

PubMed

Implant materials for orbital surgery are mainly used during orbital traumatic deformity-eliminating operations, postenucleation stump plasty, evisceration, and anophthalmic syndrome correction. There are currently a lot of biological and artificial implant materials, but there is no universal material to correct all types of defects and this makes surgeons use a great quantity of reparative procedures and techniques and scientists continue to search for more suitable implant materials. This paper reviews the currently available materials used in orbital surgery in Russia and foreign countries. PMID:21105380

Bakaeva, T V; Grusha, Ia O

2010-01-01

242

Manrating orbital transfer vehicle propulsion  

NASA Technical Reports Server (NTRS)

The expended capabilities for Orbital Transfer Vehicles (OTV) which will be needed to meet increased payload requirements for transporting materials and men to geosynchronous orbit are discussed. The requirement to provide manrating offers challenges and opportunities to the propulsion system designers. The propulsion approaches utilized in previous manned space vehicles of the United States are reviewed. The principals of reliability analysis are applied to the Orbit Transfer Vehicle. Propulsion system options are characterized in terms of the test requirements to demonstrate reliability goals and are compared to earlier vehicle approaches.

Cooper, L. P.

1985-01-01

243

Orbital, Rotational, and Climatic Interactions  

NASA Technical Reports Server (NTRS)

The report of an international meeting on the topic of Orbital, Rotational, and Climatic Interactions, which was held 9-11 Jul. 1991 at the Johns Hopkins University is presented. The meeting was attended by 22 researchers working on various aspects of orbital and rotational dynamics, paleoclimate data analysis and modeling, solid-Earth deformation studies, and paleomagnetic analyses. The primary objective of the workshop was to arrive at a better understanding of the interactions between the orbital, rotational, and climatic variations of the Earth. This report contains a brief introduction and 14 contributed papers which cover most of the topics discussed at the meeting.

Bills, Bruce G. (editor)

1992-01-01

244

Spin-Orbit Angles as a Probe to Orbital Evolution  

NASA Astrophysics Data System (ADS)

We observed with HARPS, the Rossiter-McLaughlin effect for 40 of the 75 transiting hot Jupiters discovered in the Southern Hemisphere by WASP. Our observations reveal a wide distribution in orbital inclinations indicative of past dynamical interactions. Our data also demonstrate the important effect produced by tidal interactions in shaping the spin-orbit (?) angle distribution. We briefly present and interpret the data we collected in a series of graphs.

Triaud, A. H. M. J.; Cameron, A. Collier; Queloz, D.; Anderson, D. R.; Brown, D. J. A.; Smalley, B.; Bouchy, F.; Lendl, M.; Gillon, M.

2014-01-01

245

Orbit determination and control for the European Student Moon Orbiter  

NASA Astrophysics Data System (ADS)

This paper presents the preliminary navigation and orbit determination analyses for the European Student Moon Orbiter. The severe constraint on the total mission ?v and the all-day piggy-back launch requirement imposed by the limited available budget, led to the choice of using a low-energy transfer, more specifically a Weak Stability Boundary one, with a capture into an elliptic orbit around the Moon. A particular navigation strategy was devised to ensure capture and fulfil the requirement for the uncontrolled orbit stability at the Moon. This paper presents a simulation of the orbit determination process, based on an extended Kalman filter, and the navigation strategy applied to the baseline transfer of the 2011-2012 window. The navigation strategy optimally allocates multiple Trajectory Correction Manoeuvres to target a so-called capture corridor. The capture corridor is defined, at each point along the transfer, by back-propagating the set of perturbed states at the Moon that provides an acceptable lifetime of the lunar orbit.

Zuiani, Federico; Gibbings, Alison; Vetrisano, Massimo; Rizzi, Francesco; Martinez, Cesar; Vasile, Massimiliano

2012-10-01

246

Reactionless orbital propulsion using tether deployment  

NASA Technical Reports Server (NTRS)

Examples of tether propulsion in orbit without the use of reaction mass are discussed. These include (1) using tether extension to reposition a satellite in orbit without fuel expenditure by extending a mass on the end of the tether; (2) using a tether for eccentricity pumping to add energy to the orbit for boosting and orbital transfer; and (3) length modulation of a spinning tether to transfer angular momentum between the orbit and tether spin, thus allowing changes in orbital angular momentum.

Landis, Geoffrey A.

1990-01-01

247

Two stage to orbit design  

NASA Technical Reports Server (NTRS)

A preliminary design of a two-stage to orbit vehicle was conducted with the requirements to carry a 10,000 pound payload into a 300 mile low-earth orbit using an airbreathing first stage, and to take off and land unassisted on a 15,000 foot runway. The goal of the design analysis was to produce the most efficient vehicle in size and weight which could accomplish the mission requirements. Initial parametric analysis indicated that the weight of the orbiter and the transonic performance of the system were the two parameters that had the largest impact on the design. The resulting system uses a turbofan ramjet powered first stage to propel a scramjet and rocket powered orbiter to the stage point of Mach 6 to 6.5 at an altitude of 90,000 ft.

1991-01-01

248

Pioneer Venus Orbiter Fluxgate Magnetometer  

Microsoft Academic Search

The fluxgate magnetometer on the Pioneer Venus orbiter spacecraft is described. Special features include gradiometer operation, on board despinning, a floating point processor and variable Nyquist filters. Initial operations have been entirely successful.

C. T. Russell; R. C. Snare; J. D. Means; R. C. Elphic

1980-01-01

249

Canonical elements for collision orbits  

E-print Network

I derive a set of canonical elements that are useful for collision orbits (perihelion distance approaching zero at fixed semimajor axis). The coordinates are the mean anomaly and the two spherical polar angles at aphelion.

Scott Tremaine

2000-12-12

250

Orbital Maneuvering system design evolution  

NASA Technical Reports Server (NTRS)

Preliminary design considerations and changes made in the baseline space shuttle orbital maneuvering system (OMS) to reduce cost and weight are detailed. The definition of initial subsystem requirements, trade studies, and design approaches are considered. Design features of the engine, its injector, combustion chamber, nozzle extension and bipropellant valve are illustrated and discussed. The current OMS consists of two identical pods that use nitrogen tetroxide (NTO) and monomethylhydrazine (MMH) propellants to provide 1000 ft/sec of delta velocity for a payload of 65,000 pounds. Major systems are pressurant gas storage and control, propellant storage supply and quantity measurement, and the rocket engine, which includes a bipropellant valve, an injector/thrust chamber, and a nozzle. The subsystem provides orbit insertion, circularization, and on orbit and deorbit capability for the shuttle orbiter.

Gibson, C.; Humphries, C.

1985-01-01

251

Real and Hybrid Atomic Orbitals.  

ERIC Educational Resources Information Center

Demonstrates that the Schrodinger equation for the hydrogenlike atom separates in both spheroconal and prolate spheroidal coordinates and that these separations provide a sound theoretical basis for the real and hybrid atomic orbitals. (Author/SK)

Cook, D. B.; Fowler, P. W.

1981-01-01

252

NASA Orbital Debris Baseline Populations  

NASA Technical Reports Server (NTRS)

The NASA Orbital Debris Program Office has created high fidelity populations of the debris environment. The populations include objects of 1 cm and larger in Low Earth Orbit through Geosynchronous Transfer Orbit. They were designed for the purpose of assisting debris researchers and sensor developers in planning and testing. This environment is derived directly from the newest ORDEM model populations which include a background derived from LEGEND, as well as specific events such as the Chinese ASAT test, the Iridium 33/Cosmos 2251 accidental collision, the RORSAT sodium-potassium droplet releases, and other miscellaneous events. It is the most realistic ODPO debris population to date. In this paper we present the populations in chart form. We describe derivations of the background population and the specific populations added on. We validate our 1 cm and larger Low Earth Orbit population against SSN, Haystack, and HAX radar measurements.

Krisko, Paula H.; Vavrin, A. B.

2013-01-01

253

Orbital entanglement in quantum chemistry  

E-print Network

The basic concepts of orbital entanglement and its application to chemistry are briefly reviewed. The calculation of orbital entanglement measures from correlated wavefunctions is discussed in terms of reduced $n$-particle density matrices. Possible simplifications in their evaluation are highlighted in case of seniority-zero wavefunctions. Specifically, orbital entanglement allows us to dissect electron correlation effects in its strong and weak contributions, to determine bond orders, to assess the quality and stability of active space calculations, to monitor chemical reactions, and to identify points along the reaction coordinate where electronic wavefunctions change drastically. Thus, orbital entanglement represents a useful and intuitive tool to interpret complex electronic wavefunctions and to facilitate a qualitative understanding of electronic structure and how it changes in chemical processes.

Boguslawski, Katharina

2014-01-01

254

Aqua satellite orbiting the Earth  

NASA Video Gallery

This animation shows the Aqua satellite orbiting the Earth on August 27, 2005 by revealing MODIS true-color imagery for that day. This animation is on a cartesian map projection, so the satellite w...

255

Ballistic mode Mercury orbiter missions.  

NASA Technical Reports Server (NTRS)

The MVM'73 Mercury flyby mission will initiate exploration of this unique planet. No firm plans for follow-on investigations have materialized due to the difficult performance requirements of the next logical step, an orbiter mission. Previous investigations of ballistic mode flight opportunities have indicated requirements for a Saturn V class launch vehicle. Consequently, most recent effort has been oriented to use of solar electric propulsion. More comprehensive study of the ballistic flight mode utilizing Venus gravity-assist has resulted in identification of timely high-performance mission opportunities compatible with programmed launch vehicles and conventional spacecraft propulsion technologies. A likely candidate for an initial orbiter mission is a 1980 opportunity which offers net orbiter spacecraft mass of about 435 kg with the Titan IIIE/Centaur launch vehicle and single stage solid propulsion for orbit insertion.

Hollenbeck, G. R.

1973-01-01

256

Five Planets Orbiting 55 Cancri  

E-print Network

We report 18 years of Doppler shift measurements of a nearby star, 55 Cancri, that exhibit strong evidence for five orbiting planets. The four previously reported planets are strongly confirmed here. A fifth planet is presented, with an apparent orbital period of 260 days, placing it 0.78 AU from the star in the large empty zone between two other planets. The velocity wobble amplitude of 4.9 \\ms implies a minimum planet mass \\msini = 45.7 \\mearthe. The orbital eccentricity is consistent with a circular orbit, but modest eccentricity solutions give similar \\chisq fits. All five planets reside in low eccentricity orbits, four having eccentricities under 0.1. The outermost planet orbits 5.8 AU from the star and has a minimum mass, \\msini = 3.8 \\mjupe, making it more massive than the inner four planets combined. Its orbital distance is the largest for an exoplanet with a well defined orbit. The innermost planet has a semi-major axis of only 0.038 AU and has a minimum mass, \\msinie, of only 10.8 \\mearthe, one of the lowest mass exoplanets known. The five known planets within 6 AU define a {\\em minimum mass protoplanetary nebula} to compare with the classical minimum mass solar nebula. Numerical N-body simulations show this system of five planets to be dynamically stable and show that the planets with periods of 14.65 and 44.3 d are not in a mean-motion resonance. Millimagnitude photometry during 11 years reveals no brightness variations at any of the radial velocity periods, providing support for their interpretation as planetary.

Debra A. Fischer; Geoffrey W. Marcy; R. Paul Butler; Steven S. Vogt; Greg Laughlin; Gregory W. Henry; David Abouav; Kathryn M. G. Peek; Jason T. Wright; John A. Johnson; Chris McCarthy; Howard Isaacson

2007-12-23

257

Irregular Satellites: Orbits and Origins  

Microsoft Academic Search

Each of the giant planets has irregular satellites, moons that occupy large orbits of significant eccentricity e and\\/or inclination i. Since 1997, when only 10 irregular satellites were known, 29 new ones have been discovered, allowing the dynamical structure of these systems to be discerned. The irregulars often lie close to the orbital stability limit, about 1\\/2-1\\/3 of the way

J. A. Burns; B. J. Gladman; P. D. Nicholson; R. A. Jacobson; V. Carruba; M. J. Holman; JJ Kavelaars

2001-01-01

258

Multimodality imaging of the orbit  

PubMed Central

The role of imaging is well established in the evaluation of orbital diseases. Ultrasonography, Computed tomography and Magnetic resonance imaging are complementary modalities, which allow direct visualization of regional anatomy, accurate localization and help to characterize lesions to make a reliable radiological diagnosis. The purpose of this pictorial essay is to highlight the imaging features of commonly encountered pathologies which involve the orbit. PMID:23599570

Hande, Pradipta C; Talwar, Inder

2012-01-01

259

Orbital motion in stellar systems  

NASA Astrophysics Data System (ADS)

Researchers investigated the possibility of developing an angle action representation of the motion of stars in potentials that approximate to those of elliptical galaxies. The method is based on the observation that the Fourier amplitudes of the spectral decomposition of coordinate motion decreases asymptotically for a variety of orbits in integral and near-integral two dimensional potential. Analytic results for motion in a one dimensional Kepler potential support this conclusion. The researchers therefore choose to approximate the series of Fourier amplitudes by a geometric sum. They found that the rational approximation to Fourier series is a considerable improvement upon present techniques for eccentric orbits. The orbit representation is then fitted to the orbit's phase-space torus via an iterative scheme similar to that of Ratcliff, Chang and Swarzschild (1984). The major work here concerns the construction and modification of this scheme to enable convergence of the initial representation to an accurate orbital solution. The results indicate that the representation is indeed capable of accurately depicting short-axis tube orbits in integrable and near-integrable potentials.

Binks, P. N.

260

Mars Observer Orbit Insertion Briefing  

NASA Technical Reports Server (NTRS)

For the first part of this briefing, see NONP-NASA-VT-2000081556. Marvin Traxler continues his discussion on signal tracking from the Mars Observer. Julie Webster, Lead Engineer, Telecommunications Subsystem, is introduced. She explains how signals coming back from Mars are detected. Dr. Pasquale Esposito talks about flyby orbits and capture orbits. He says that frequencies coming from the spacecraft can determine if the spacecraft has flown by Mars, or if a capture orbit has occurred. Charles Whetsel, System Engineer Spacecraft Team, presents a computer program. He shows where the signal will appear on the computer from the Spacecraft. Suzanne Dodd presents orbit insertion geometry. Dr. Arden Albee, Project Scientist Mars Observer Project, Cal Tech tech, says that Mars is studied to get more data to confirm their hypotheses derived from previous Mars Missions such as the Viking Mars Program and the Mariner Program. Dr. Albee also describes instrumentation on the Mars Observer such as the Ultra Stable Oscillator, Mars Orbiter Laser Altimeter, and Magnetometer. The camera on the spacecraft is similar to a fax machine because it scans one line at a time as the spacecraft orbits Mars. Dr. Michael Malin, Principle Investigator Mars Observer Camera, Malin Space Science Systems, Inc., describe this process.

1993-01-01

261

Modeling issues in precision orbit determination for Mars orbiter  

NASA Technical Reports Server (NTRS)

This paper examines the accuracy of recent Mars gravity models and the importance of perturbations due to the Mars radiation pressure and the Martian moons, Phobos and Deimos, on the trajectories of Mars orbiters. A linear orbit perturbation theory is used to characterize the patterns of gravity field near resonances for the Viking and Mariner 9 spacecraft. These resonances are shown to have considerable power and their potential for contributing to Mars gravity solutions is emphasized. It is shown that some of the same resonance orders which appear in the Viking orbits, dominate the radial orbit error spectrum for Mars Observer. Results of orbit determination simulations at the Goddard Space Flight Center show that the perturbations caused by the Martian moons and the Mars radiation pressure are larger than 0.1 mm/s, the expected precision of the Mars Observer Doppler tracking data. Tests with the Viking Doppler data indicate that best analysis of these data mandates the inclusion of the Phobos gravitational perturbation in the modeling of Viking spacecraft trajectories.

Lemoine, Frank G.; Rosborough, George W.; Smith, David E.

1990-01-01

262

A New NOAO Survey Program: Mutual Orbits and Masses of Kuiper Belt Binaries  

NASA Astrophysics Data System (ADS)

We will report progress from our multi-year campaign to determine the orbits and masses of transneptunian binaries (TNBs). Binary systems are abundant in the Kuiper belt, and especially among the "Cold Classical" disk of objects on low-eccentricity, lowinclination, non-resonant orbits about the Sun [1]. These binaries offer an opportunity to learn the masses and densities of an intriguing population of small, distant objects. Additionally, the statistics of their mutual orbital parameters offer clues to conditions where they formed in the protoplanetary nebula, as well as to subsequent dynamical evolution of the outer solar system. Historically, NASA/ESA's Hubble Space Telescope (HST) has been the premier facility for spatially resolving the components of TNBs, benefiting from its exceptionally stable optics and from diffraction- limited imaging unimpeded by the Earth's atmosphere. More recently, laser guide star adaptive optics (LGS AO) technology has enabled large groundbased telescopes to begin contributing valuable data as well [2]. LGS AO observations of faint TNBs (the components of which have typical V magnitudes ~24th) are only feasible when the target passes near an appulse star suitable for use as a tip-tilt correction reference. We have been using LGS AO data from Keck in combination with HST data to constrain TNB orbits [e.g., 3]. In 2011 we began a new 3-year NOAO Survey program to use LGS AO on the 8 m Gemini North telescope. We will discuss how Gemini and other telescopes complement one another, show examples of data from Gemini, Keck, and HST, and describe how we are using these facilities to improve orbital knowledge for as many of the tighter TNBs as we can. Optimal scheduling techniques enable us to make the most efficient possible use of the very limited availability of time on telescopes capable of resolving these objects [4]. Our progress is documented online at http://www.lowell.edu/~grundy/tnbs. We will discuss systems of particular interest such as those likely to undergo mutual events in the near future. These include 2003 QW111 (events probably beginning in a few years) and 79360 1997 CS29 (events probably happening right now). Also of interest are systems for which sizes can be independently determined from thermal or other observations. For these systems, the dynamical masses from binary orbits enable computation of bulk densities. We will also explore statistical patterns beginning to emerge from the growing ensemble of known TNB orbits. Observed distributions of orbital characteristics, including inclinations, eccentricities, and separations have important implications for formation scenarios as well as subsequent evolution [5], although accounting for observational biases remains an open issue. For instance, there appears to be a shortage of loose binaries among TNOs on excited heliocentric orbits. While there seems to be an excess of prograde systems among the tighter binaries, there is little evidence for preferentially low inclinations.

Grundy, W. M.; Benecchi, S. D.; Buie, M. W.; Noll, K. S.; Porter, S. B.; Roe, H. G.; Stansberry, J. A.; Trujillo, C. A.

2011-10-01

263

A criterion to classify asteroids and comets based on the orbital parameters  

NASA Astrophysics Data System (ADS)

The classification criterion between asteroids and comets has evolved in recent decades, but the main distinction remains unchanged. Comets present gas and dust ejection from the surface at some point of their orbits, therefore, these objects are considered to be active. On the other hand, asteroids do not show any kind of large scale gas and dust ejection, they are inert. Nevertheless, this classification scheme is impractical when we have more than 500,000 asteroids already discovered. In addition, comets are not active all along their orbits. In order for a comet to display activity at present or in the recent past in the inner region of the Solar System (heliocentric distance <2 AU), the cometary orbit must be unstable in the time scale on the order of ten thousands of years; otherwise, the object should have completely consumed its volatile component. Close encounters with the most massive planets is the only mechanism that could produce “macroscopic” instabilities on a short time scale. The macroscopic changes in the orbital elements can be detected in a numerical integration of the dynamical evolution of the object over a time scale of several thousand years. This procedure to identify asteroids in cometary-like orbits is also impractical because it would require months of computing time. Therefore, a classification scheme based on the orbital elements to identify the border cases between the asteroid and comet populations is urgently required. We present a criterion to classify asteroids and comets and to find the border case based on the Tisserand’s parameter, the Minimum Orbital Intersection Distance (MOID), and considering some information regarding the aphelion and perihelion distances. Objects in mean-motion are disregarded. After applying a filter to the sample of over half a million asteroids already discovered to select the precise orbits and to the sample of 487 short-period comets, we apply the proposed classification criterion. The resulting sample consists of ?331 Asteroids in Cometary Orbits (ACOs). The ACOs are further classified in subclasses similar to the cometary classification. There are 436 Jupiter Family Comets and 203 ACOs of the Jupiter Family type. This new criterion is more strict that the criteria used by other authors to identify ACOs; nonetheless, with the new criterion we ensure that the ACOs have a chaotic dynamical evolution similar to the periodic comets. The discovered dormant or extinct comets seems, if they exist at all, to be a small fraction of the active comets. We also analyse the available photometric data of ACOs to identify possible large brightness variations. Among the sample of ACOs, there is only one object with brightness variations typical of an active comet: 174P/(60558) Echeclus. But this object has already been double classified as asteroid and comet.

Tancredi, Gonzalo

2014-05-01

264

Galileo Probe delivery and Orbiter approach orbit determination  

NASA Technical Reports Server (NTRS)

The configuration of the Galileo mission, in which the Probe and Orbiter are joined as a single spacecraft (until five months before Jupiter encounter, when the Probe will be released into the atmosphere for the Io flyby) is discussed, together with the major mission objectives, and the aspects of the trajectory. Special attention is given to the descriptions of the orbit determination process, error source assumptions (based on the Voyager experience at Jupiter), and data assumptions. The orbit determination results for the interplanetary and Jupiter approach phases of the mission for the previously planned launch in 1986 are presented, together with the preliminary results of navigation studies of the current mission scheduled for a launch for late 1989.

Kenyon, P. R.; Moultrie, B.; Kechichian, J. A.; Nicholson, F. T.

1987-01-01

265

Spin-orbit angles as a probe to orbital evolution  

NASA Astrophysics Data System (ADS)

The WASP (Wide Angle Search for Planets) has discovered 75 planets in the Southern Hemisphere. We followed-up 40 of these and observed the Rossiter-McLaughlin effect. It allows us to measure the angle between the stellar spin and the planet's orbital spin. Here, we present the results of our survey, along with results published in the literature. Our observations reveal a wide distribution in orbital angle, indicative or past dynamical interactions. Our data also demonstrates the important effects that tidal interactions have in altering the spin-orbit distribution. This renders any interpretation tricky. However, comparing different sub-samples we start uncovering evidence that two types of migration are maybe acting to create the hot Jupiter population.

Triaud, Amaury; Collier Cameron, Andrew; Queloz, Didier; Anderson, David; Brown, David; Smalley, Barry; Bouchy, Francois; Lendl, Monika; Gillon, Michael

2013-07-01

266

Recurrence plots and unstable periodic orbits  

Microsoft Academic Search

Chaotic attractors contain an infinity of unstable periodic orbits. These orbits are interesting not only because they represent an element of order within chaos, but also be- cause they make up the skeleton of the attractor, and in an easily formalized way. An orbit on a chaotic attractor, in particular, is the closure of the set of unstable periodic orbits,

Elizabeth Bradley; Ricardo Mantilla

2005-01-01

267

Orbit stabilization in SPring8 storage ring  

Microsoft Academic Search

Stability of electron orbit is one of the most important properties to achieve brilliant photon beams for third generation synchrotron radiation sources. In the design of a SPring-8 storage ring, many ideas for orbit stabilization were thus considered. Consequently, without any correction, electron orbit stability of about 50 ?m per day is obtained. Since a main part of the orbit

N. Kumagai; H. Ohkuma; K. Soutome; M. Takao; H. Tanaka

1999-01-01

268

Planetary orbits in multiple star systems  

Microsoft Academic Search

The orbital stability and origin of planetary orbits in multiple star systems are considered in relation to the possibility of life existing on planets in such systems. Results of statistical studies of orbital stability in a range of multiple systems are presented which indicate that a planet can stay in a stable orbit in a (visual) binary system if it

R. S. Harrington

1981-01-01

269

Optimal parking orbits for manned Mars missions  

Microsoft Academic Search

This paper summarizes a Mars parking orbit optimization effort. This parking orbit study includes the selection of optimal elliptic Mars parking orbits that meet mission constraints and that include pertinent apsidal misalignment losses. Mars missions examined are for the opportunity years of 2014, 2016, and 2018. For these mission opportunities, it is shown that the optimal parking orbits depend on

Michael L. Cupples; Jill A. Nordwall

1993-01-01

270

Evaluation of viewing periods between orbiting spacecraft  

NASA Technical Reports Server (NTRS)

Communication links between two orbiters are analyzed by projecting occultation regions onto the orbit planes. The occultation regions are conic sections, and can be defined in the same functional form as orbits. Cases of a full and partial ellipse, full, partial, and degenerate hyperbola, and parabola are considered. It is noted that because overall communication link availability may depend on earth-to-orbiter and surface-to-orbiter links, the analysis must consider the simultaneous performance of all links. The approach presented in this study gives insight into the orbiter-to-orbiter geometry and the overall communication link availability.

Meyer, Scott A.

1989-01-01

271

Overview of Venus orbiter, Akatsuki  

NASA Astrophysics Data System (ADS)

The Akatsuki spacecraft of Japan was launched on May 21, 2010. The spacecraft planned to enter a Venus-encircling near-equatorial orbit in December 7, 2010; however, the Venus orbit insertion maneuver has failed, and at present the spacecraft is orbiting the Sun. There is a possibility of conducting an orbit insertion maneuver again several years later. The main goal of the mission is to understand the Venusian atmospheric dynamics and cloud physics, with the explorations of the ground surface and the interplanetary dust also being the themes. The angular motion of the spacecraft is roughly synchronized with the zonal flow near the cloud base for roughly 20 hours centered at the apoapsis. Seen from this portion of the orbit, cloud features below the spacecraft continue to be observed over 20 hours, and thus the precise determination of atmospheric motions is possible. The onboard science instruments sense multiple height levels of the atmosphere to model the three-dimensional structure and dynamics. The lower clouds, the lower atmosphere and the surface are imaged by utilizing near-infrared windows. The cloud top structure is mapped by using scattered ultraviolet radiation and thermal infrared radiation. Lightning discharge is searched for by high speed sampling of lightning flashes. Night airglow is observed at visible wavelengths. Radio occultation complements the imaging observations principally by determining the vertical temperature structure.

Nakamura, M.; Imamura, T.; Ishii, N.; Abe, T.; Satoh, T.; Suzuki, M.; Ueno, M.; Yamazaki, A.; Iwagami, N.; Watanabe, S.; Taguchi, M.; Fukuhara, T.; Takahashi, Y.; Yamada, M.; Hoshino, N.; Ohtsuki, S.; Uemizu, K.; Hashimoto, G. L.; Takagi, M.; Matsuda, Y.; Ogohara, K.; Sato, N.; Kasaba, Y.; Kouyama, T.; Hirata, N.; Nakamura, R.; Yamamoto, Y.; Okada, N.; Horinouchi, T.; Yamamoto, M.; Hayashi, Y.

2011-05-01

272

Tumor pathology of the orbit.  

PubMed

The term orbital tumor covers a wide range of benign and malignant diseases affecting specific component of the orbit or developing in contact with them. They are found incidentally or may be investigated as part of the assessment of a systemic disorder or because of orbital signs (exophthalmos, pain, etc.). Computed tomography, MRI and Color Doppler Ultrasound (CDU), play a varying role depending on the clinical presentation and the disease being investigated. This article reflects long experience in a reference center but does not claim to be exhaustive. We have chosen to consider these tumors from the perspective of their usual presentation, emphasizing the most common causes and suggestive radiological and clinical presentations (progressive or sudden-onset exophthalmos, children or adults, lacrimal gland lesions, periorbital lesions and enophthalmos). We will describe in particular muscle involvement (thyrotoxicosis and tumors), vascular lesions (cavernous sinus hemangioma, orbital varix, cystic lymphangioma), childhood lesions and orbital hematomas. We offer straightforward useful protocols for simple investigation and differential diagnosis. Readers who wish to go further to extend their knowledge in this fascinating area can refer to the references in the bibliography. PMID:25195185

Héran, F; Bergès, O; Blustajn, J; Boucenna, M; Charbonneau, F; Koskas, P; Lafitte, F; Nau, E; Roux, P; Sadik, J C; Savatovsky, J; Williams, M

2014-10-01

273

LOP - Long-Term Orbit Predictor  

NASA Technical Reports Server (NTRS)

Long-Term Orbit Preditor (LOP) trajectory-propagation computer program is useful tool in analysis of lifetime of orbiting spacecraft. Suitable for studying planetary-orbit missions with reconnaissance (flyby) and exploratory (mapping) trajectories. Includes sample data for study of drift cycle of geosynchronous station, strategy for radar mapping of Venus, frozen orbit about Mars, and orbit characterized by repeating ground trace. Executed faster than such programs based on Cowell's method. Written in FORTRAN 77.

Kwok, Johnny H.

1992-01-01

274

Orbital, Rotational, and Climatic Interactions  

SciTech Connect

The report of an international meeting on the topic of Orbital, Rotational, and Climatic Interactions, which was held 9-11 Jul. 1991 at the Johns Hopkins University is presented. The meeting was attended by 22 researchers working on various aspects of orbital and rotational dynamics, paleoclimate data analysis and modeling, solid-Earth deformation studies, and paleomagnetic analyses. The primary objective of the workshop was to arrive at a better understanding of the interactions between the orbital, rotational, and climatic variations of the Earth. This report contains a brief introduction and 14 contributed papers which cover most of the topics discussed at the meeting. Separate abstracts have been prepared for articles from this report.

Bills, B.G.

1992-12-01

275

The Challenge of Orbital Debris  

NASA Technical Reports Server (NTRS)

Since the dawn of the Space Age more than 50 years ago, humans have been launching objects into the space environment faster than they have been removed by active means or natural decay. This has led to a proliferation of debris -- derelict satellites, discarded rocket upper stages, and pieces from satellite breakups -- in Earth orbit, especially in well-used orbital regimes. This talk will summarize the current knowledge of the debris environment and describe plans to address the challenges orbital debris raises for the future usability of near-Earth space. The talk will be structured around 4 categories: Measurements, Modeling, Shielding, and Mitigation. This will include discussions of the long-term prognosis of debris growth (i.e., the "Kessler Syndrome") as well as plans for active debris removal.

Matney, Mark

2012-01-01

276

Spin-orbital driven ferroelectricity  

NASA Astrophysics Data System (ADS)

We study the effect of octahedron rotation on the electric polarization with spin-orbit coupling. Employing local coordinates to represent the tilting of the ligands' octahedra, we evaluate the electric polarization in a chain of transition metal ions with non-polar octahedron rotation. We find the orbital ordering produced by the ligands' rotation and the spin order, together, determine the polarization features, manifesting that non-vanishing polarization appears in collinear spin order and the direction of polarization is no more restricted in the plane of spin rotation in cycloidal ordering.

Zhu, Shan; Li, You-Quan

2014-10-01

277

Current Issues in Orbital Debris  

NASA Technical Reports Server (NTRS)

During the past two decades, great strides have been made in the international community regarding orbital debris mitigation. The majority of space-faring nations have reached a consensus on an initial set of orbital debris mitigation measures. Implementation of and compliance with the IADC and UN space debris mitigation guidelines should remain a high priority. Improvements of the IADC and UN space debris mitigation guidelines should continue as technical consensus permits. The remediation of the near-Earth space environment will require a significant and long-term undertaking.

Johnson, Nicholas L.

2011-01-01

278

Orbit and properties of the massive X-ray binary BD +60 73=IGR J00370+6122  

NASA Astrophysics Data System (ADS)

Context. High-energy X-rays generated in massive binary systems can arise from several different mechanisms. Constraints on the orbital parameters of these systems are therefore necessary to properly understand and interpret the X-ray phenomena. Aims: In this study we aim to determine a spectroscopic orbit for the high-mass X-ray binary system BD +60 73=IGR J00370+6122, to infer the properties of the optical and compact companion, and to interpret the characteristics of the X-ray light curve within the context of our findings. Methods: We acquired 123 spectroscopic observations with the David Dunlap Observatory and Kitt Peak National Observatory telescopes in the optical domain. Using a cross-correlation technique, we measured the radial velocity of each of these spectra relative to the heliocentric rest-frame. An orbital solution was obtained from the resulting radial velocity measurements. Spectra of several spectral standards were also acquired to reassess the spectral classification of the optical companion. Results: The best-fit orbital parameters suggest an eccentricity of e = 0.48+0.02-0.03 and a mass-function of f(M) = 0.009 ± 0.002, lending further support to the assumption that the companion is a low-mass compact star. We find that the X-ray maximum occurs just after the time of periastron passage, but before the time of superior conjunction when the optical companion could eclipse the compact companion. The spectrum of the optical companion is best matched by the B1Ib spectral standard HD 24398, which reaffirms the original classification. Conclusions: The mass-function combined with a plausible range of possible masses for a neutron star companion yields primary masses within the range expected for the spectral type of BD +60 73 for high orbital inclinations. The compact companion cannot be a black hole unless the supergiant has an exceptionally high mass for its B1Ib spectral type or if the inclination of its orbit is very low. The X-ray timing and characteristics can potentially be explained by accretion variations on the compact object; but this would require the companion to be a magnetar. Table 2 is available in electronic form at http://www.aanda.org

Grunhut, J. H.; Bolton, C. T.; McSwain, M. V.

2014-03-01

279

Orbital blowout fractures in sport  

Microsoft Academic Search

One-third of orbital blowout fractures are sustained during sport. Soccer is most commonly involved. Though visual acuity recovery is usually complete, permanent loss of binocular visual field is almost universal. Typically high-energy blows by opponent's finger, fist, elbow, knee or boot are responsible. Injuries to the eye itself may also be sustained and should be looked for. Ocular protection may

N P Jones

1994-01-01

280

Revised orbital parameters for planets  

Microsoft Academic Search

Orbital parameters of planets are fitted directly to an appropriate set of observations. It is shown how to use the rigorous Deming method combined with a numerical integration of gravitation equations. In all, 65 parameters of the nine planets (masses and initial positions and velocities at J2000) are listed. The complete set of their standard errors, and the associated variance-covariance

A. C. Lefloch

2002-01-01

281

Orbiter thermal control subsystem development  

NASA Technical Reports Server (NTRS)

Selected major hardware components and subsystems of the shuttle orbiter are described. These include the hardware configurations, development problems and solutions, performance requirements and attainment, major hardware fabrication problems and solutions, development test objectives and implementation, and utilization of test results for hardware refinements. The subsystems selected for discussion are the space radiator, the ammonia boiler, the flash evaporator, and avionics cold plates.

Laubach, G. E.

1978-01-01

282

Getting a Crew into Orbit  

ERIC Educational Resources Information Center

Despite the temporary setback in our country's crewed space exploration program, there will continue to be missions requiring crews to orbit Earth and beyond. Under the NASA Authorization Act of 2010, NASA should have its own heavy launch rocket and crew vehicle developed by 2016. Private companies will continue to explore space, as well. At the…

Riddle, Bob

2011-01-01

283

Autonomous perturbations of LISA orbits  

NASA Astrophysics Data System (ADS)

We investigate autonomous perturbations on the orbits of LISA, namely the effects produced by gravitational fields that can be expressed only in terms of the position, but not of time in the Hill frame. This first step in the study of the LISA orbits has been the subject of recent papers which implement analytical techniques based on a 'post-epicyclic' approximation in the Hill frame to find optimal unperturbed orbits. The natural step forward is to analyze the perturbations to purely Keplerian orbits. In this work, a particular emphasis is put on the tidal field of the Earth assumed to be stationary in the Hill frame. Other relevant classes of autonomous perturbations are those given by the corrections to the solar field responsible for a slow precession and a global stationary field, associated with sources such as the interplanetary dust or a local dark matter component. The inclusion of simple linear contributions in the expansion of these fields produces secular solutions that can be compared with the measurements and possibly used to evaluate some morphological property of the perturbing components.

Pucacco, G.; Bassan, M.; Visco, M.

2010-12-01

284

Comet Odyssey: Comet Nucleus Orbiter  

Microsoft Academic Search

Comet Odyssey is a comet nucleus orbiter mission, proposed to NASA's Discovery program in 2004. The goal of the mission is to completely characterize a cometary nucleus, both physically and compositionally, as can only be done during an extended rendezvous and not with a fast flyby. Comet Odyssey will launch in October 2009 on a Delta II 7925 and use

P. R. Weissman; W. D. Smythe; S. J. Spitz; D. E. Bernard; R. W. Bailey

2004-01-01

285

Viking orbiter views of Mars  

Microsoft Academic Search

Images acquired by the Viking orbiters, beginning in 1976 are presented. The pictures represent only a small fraction of the many thousands taken, and were chosen to illustrate the diverse geology of Mars and its atmospheric phenomena. Specific topics discussed include the Viking mission and its objectives, a brief comparison of Earth and Mars, and surface features of Mars including

M. H. Carr; W. A. Baum; K. R. Blasius; G. A. Briggs; J. A. Cutts; T. C. Duxbury; R. Greeley; J. Guest; H. Masursky; B. A. Smith

1980-01-01

286

Removing Orbital Debris with Lasers  

E-print Network

Orbital debris in low Earth orbit (LEO) are now sufficiently dense that the use of LEO space is threatened by runaway collisional cascading. A problem predicted more than thirty years ago, the threat from debris larger than about 1 cm demands serious attention. A promising proposed solution uses a high power pulsed laser system on the Earth to make plasma jets on the objects, slowing them slightly, and causing them to re-enter and burn up in the atmosphere. In this paper, we reassess this approach in light of recent advances in low-cost, light-weight modular design for large mirrors, calculations of laser-induced orbit changes and in design of repetitive, multi-kilojoule lasers, that build on inertial fusion research. These advances now suggest that laser orbital debris removal (LODR) is the most cost-effective way to mitigate the debris problem. No other solutions have been proposed that address the whole problem of large and small debris. A LODR system will have multiple uses beyond debris removal. Internat...

Phipps, Claude R; Bradford, Brian; George, E Victor; Libby, Stephen B; Liedahl, Duane A; Marcovici, Bogdan; Olivier, Scot S; Pleasance, Lyn D; Reilly, James P; Rubenchik, Alexander; Strafford, David N; Valley, Michael T

2011-01-01

287

APPROXIMATE SYMMETRIES OF INTERPLANETARY ORBIT  

E-print Network

science experiment of the BepiColombo mission to the planet Mercury shall allow to solve for the gravity field of the planet up to degree and order 25, for an improved orbit of Mercury and a very accurate, providing results adequate for the achievement of the mission science goals. BepiColombo is the next

Milani, Andrea

288

Pioneer Venus Orbiter fluxgate magnetometer  

Microsoft Academic Search

A fluxgate magnetometer on the Pioneer Venus Orbiter spacecraft is described. Consideration is given to system design, construction, and initial operation. Emphasis is placed on such features as gradiometer operation, on-board despinning, a floating-point processor, and variable Nyquist filters.

C. T. Russell; R. C. Snare; J. D. Means; R. C. Elphic

1980-01-01

289

Augmented orbiter heat rejection study  

NASA Technical Reports Server (NTRS)

Spacecraft radiator concepts are presented that relieve attitude restrictions required by the shuttle orbiter space radiator for baseline and extended capability STS missions. Cost effective heat rejection kits are considered which add additional capability in the form of attached spacelab radiators or a deployable radiator module.

Hixon, C. W.

1981-01-01

290

Orbital Debris Research at NASA  

NASA Technical Reports Server (NTRS)

The United States has one of the most active programs of research of the orbital debris environment in the world. Much of the research is conducted by NASA s Orbital Debris Program Office at the Johnson Space Center. Past work by NASA has led to the development of national space policy which seeks to limit the growth of the debris population and limit the risk to spacecraft and humans in space and on the Earth from debris. NASA has also been instrumental in developing consistent international policies and standards. Much of NASA's efforts have been to measure and characterize the orbital debris population. The U.S. Department of Defense tracks and catalogs spacecraft and large debris with it's Space Surveillance Network while NASA concentrates on research on smaller debris. In low Earth orbit, NASA has utilized short wavelength radars such as Haystack, HAX, and Goldstone to statistically characterize the population in number, size, altitude, and inclination. For higher orbits, optical telescopes have been used. Much effort has gone into the understanding and removal of observational biases from both types of measurements. NASA is also striving to understand the material composition and shape characteristics of debris to assess these effects on the risk to operational spacecraft. All of these measurements along with data from ground tests provide the basis for near- and long-term modeling of the environment. NASA also develops tools used by spacecraft builders and operators to evaluate spacecraft and mission designs to assess compliance with debris standards and policies which limit the growth of the debris environment.

Stansbery, Eugene G.

2009-01-01

291

d Orbitals in an Octahedral Ligand Field  

NSDL National Science Digital Library

Here is a page that shows the d orbitals in an axis set. Running the mouse over an orbital reveals the "name" of that orbital. This is good practice for helping students link the name of an orbital to the orientation. This page is linked to an interactive 3-dimensional applet, similar to the one above, that shows the d orbitals in an octahedral ligand field. The user may also click on the name of any one of the d orbitals to obtain a larger 3-dimensional image. The images are rotatable and scalable.

292

Thermal properties of comet 67P derived from Rosetta/VIRTIS, and orbital observations of Philae landing site  

NASA Astrophysics Data System (ADS)

The Rosetta spacecraft has reached its final target, comet 67P/Churyumov-Gerasimenko, in early August 2014. The VIRTIS imaging spectrometer onboard the Rosetta orbiter has intensively observed both the nucleus and the coma environment in the 0.25-5 microns wavelength range. Nucleus observations are performed with both channels: VIRTIS-M for spectral mapping and VIRTIS-H for high spectral resolution. Dayside surface temperatures in various illumination conditions can be retrieved from the long wavelength range. This allows us to infer local thermal properties. The very irregular shape of 67P results in unusual patterns in the heating / cooling regime of the object, e.g. sudden transitions from day to night. We will present thermal analyses of observations performed during the first mapping phase of the pre-landing activity (August 2014), with a focus on thermo-physical modeling of comet 67P on both regional and local scales, and a special emphasis on the expected landing site. These observations document the state of the comet surface at a time of large heliocentric distance and low activity. The authors acknowledge funding from CNES, ASI, and DLR, the French, Italian and German Space Agencies. Support from the Rosetta and VIRTIS science, instrument, and operation teams is gratefully acknowledged.

Drossart, Pierre; Leyrat, C.; Erard, S.; Capria, M. T.; Capaccioni, F.; Filacchione, G.; Tosi, F.; De Sanctis, M. C.; Arnold, G.; Markus, K.; Bockelée-Morvan, D.; Schmitt, B.; Formisano, M.; Kuehrt, E.

2014-11-01

293

Conversion of Osculating Orbital Elements to Mean Orbital Elements  

NASA Technical Reports Server (NTRS)

Orbit determination and ephemeris generation or prediction over relatively long elapsed times can be accomplished with mean elements. The most simple and efficient method for orbit determination, which is also known as epoch point conversion, performs the conversion of osculating elements to mean elements by iterative procedures. Previous epoch point conversion methods are restricted to shorter elapsed times with linear convergence. The new method presented in this paper calculates an analytic initial guess of the unknown mean elements from a first order theory of secular perturbations and computes a transition matrix with accurate numerical partials. It thereby eliminates the problem of an inaccurate initial guess and an identity transition matrix employed by previous methods. With a good initial guess of the unknown mean elements and an accurate transition matrix, converging osculating elements to mean elements can be accomplished over long elapsed times with quadratic convergence.

Der, Gim J.; Danchick, Roy

1996-01-01

294

Orbits and Interiors of Planets  

NASA Astrophysics Data System (ADS)

The focus of this thesis is a collection of problems of timely interest in orbital dynamics and interior structure of planetary bodies. The first three chapters are dedicated to understanding the interior structure of close-in, gaseous extrasolar planets (hot Jupiters). In order to resolve a long-standing problem of anomalously large hot Jupiter radii, we proposed a novel magnetohydrodynamic mechanism responsible for inflation. The mechanism relies on the electro-magnetic interactions between fast atmospheric flows and the planetary magnetic field in a thermally ionized atmosphere, to induce electrical currents that flow throughout the planet. The resulting Ohmic dissipation acts to maintain the interior entropies, and by extension the radii of hot Jupiters at an enhanced level. Using self-consistent calculations of thermal evolution of hot Jupiters under Ohmic dissipation, we demonstrated a clear tendency towards inflated radii for effective temperatures that give rise to significant ionization of K and Na in the atmosphere, a trend fully consistent with the observational data. Furthermore, we found that in absence of massive cores, low-mass hot Jupiters can over-flow their Roche-lobes and evaporate on Gyr time-scales, possibly leaving behind small rocky cores. Chapters four through six focus on the improvement and implications of a model for orbital evolution of the solar system, driven by dynamical instability (termed the "Nice" model). Hydrodynamical studies of the orbital evolution of planets embedded in protoplanetary disks suggest that giant planets have a tendency to assemble into multi-resonant configurations. Following this argument, we used analytical methods as well as self-consistent numerical N-body simulations to identify fully-resonant primordial states of the outer solar system, whose dynamical evolutions give rise to orbital architectures that resemble the current solar system. We found a total of only eight such initial conditions, providing independent constraints for the solar system's birth environment. Next, we addressed a significant drawback of the original Nice model, namely its inability to create the physically unique, cold classical population of the Kuiper Belt. Specifically, we showed that a locally-formed cold belt can survive the transient instability, and its relatively calm dynamical structure can be reproduced. The last four chapters of this thesis address various aspects and consequences of dynamical relaxation of planetary orbits through dissipative effects as well as the formation of planets in binary stellar systems. Using octopole-order secular perturbation theory, we demonstrated that in multi-planet systems, tidal dissipation often drives orbits onto dynamical "fixed points," characterized by apsidal alignment and lack of periodic variations in eccentricities. We applied this formalism towards investigating the possibility that the large orbital eccentricity of the transiting Neptune-mass planet Gliese 436b is maintained in the face of tidal dissipation by a second planet in the system and computed a locus of possible orbits for the putative perturber. Following up along similar lines, we used various permutations of secular theory to show that when applied specifically to close-in low-mass planetary systems, various terms in the perturbation equations become separable, and the true masses of the planets can be solved for algebraically. In practice, this means that precise knowledge of the system's orbital state can resolve the sin( i) degeneracy inherent to non-transiting planets. Subsequently, we investigated the onset of chaotic motion in dissipative planetary systems. We worked in the context of classical secular perturbation theory, and showed that planetary systems approach chaos via the so-called period-doubling route. Furthermore, we demonstrated that chaotic strange attractors can exist in mildly damped systems, such as photo-evaporating nebulae that host multiple planets. Finally, we considered planetary formation in highly inclined binary systems,

Batygin, Konstantin

2012-05-01

295

Atmosphere and orbital stability of exosolar planets orbiting gamma Cephei  

Microsoft Academic Search

The recently discovered Jupiter-like planet (m sin i= 1.76 M_jup) in the binary system gamma Cephei moves in a so-called S-type orbit around its host-star with a distance of about 2.15 AU. It is the first planet that have been found in a close binary and is from the dynamical point of view a very stable configuration. Numerical computations in

H. Lammer; R. Dvorak; E. Pilat-Lohinger; B. Funk; F. Freistetter; I. Ribas; F. Selsis; E. F. Guinan; W. W. Weiss; S. J. Bauer

2003-01-01

296

Indirect orbital floor fractures: a meta-analysis.  

PubMed

Orbit fractures are common in the context of orbital trauma. Fractures of the orbital floor without orbital rim involvement are known as indirect orbital floor fractures, pure internal floor fractures, and orbital blowout fractures. In this paper, we have reported a meta-analysis of orbital floor fractures focusing on indications and timing of surgical repair, outcomes, and complications. PMID:20616920

Gonzalez, Mithra O; Durairaj, Vikram D

2010-04-01

297

Orbital evolution around irregular bodies  

NASA Astrophysics Data System (ADS)

The new profiles of the space missions aimed at asteroids and comets, moving from fly-bys to rendezvous and orbiting, call for new spaceflight dynamics tools capable of propagating orbits in an accurate way around these small irregular objects. Moreover, interesting celestial mechanics and planetary science problems, requiring the same sophisticated tools, have been raised by the first images of asteroids (Ida/Dactyl, Gaspra and Mathilde) taken by the Galileo and NEAR probes, and by the discovery that several near-Earth asteroids are probably binary. We have now developed two independent codes which can integrate numerically the orbits of test particles around irregularly shaped primary bodies. One is based on a representation of the central body in terms of "mascons" (discrete spherical masses), while the other one models the central body as a polyhedron with a variable number of triangular faces. To check the reliability and performances of these two codes we have performed a series of tests and compared their results. First we have used the two algorithms to calculate the gravitational potential around non-spherical bodies, and have checked that the results are similar to each other and to those of other, more common, approaches; the polyhedron model appears to be somewhat more accurate in representing the potential very close to the body's surface. Then we have run a series of orbit propagation tests, integrating several different trajectories of a test particle around a sample ellipsoid. Again the two codes give results in fair agreement with each other. By comparing these numerical results to those predicted by classical perturbation formulae, we have noted that when the orbit of the test particle gets close to the surface of the primary, the analytical approximations break down and the corresponding predictions do not match the results of the numerical integrations. This is confirmed by the fact that the agreement gets better and better for orbits farther away from the primary. Finally, we have found that in terms of CPU time requirements, the performances of the two codes are quite similar, and that the optimal choice probably depends on the specific problem under study.

Rossi, A.; Marzari, F.; Farinella, P.

1999-11-01

298

Rational orbits around charged black holes  

SciTech Connect

We show that all eccentric timelike orbits in Reissner-Nordstroem spacetime can be classified using a taxonomy that draws upon an isomorphism between periodic orbits and the set of rational numbers. By virtue of the fact that the rationals are dense, the taxonomy can be used to approximate aperiodic orbits with periodic orbits. This may help reduce computational overhead for calculations in gravitational wave astronomy. Our dynamical systems approach enables us to study orbits for both charged and uncharged particles in spite of the fact that charged particle orbits around a charged black hole do not admit a simple one-dimensional effective potential description. Finally, we show that comparing periodic orbits in the Reissner-Nordstroem and Schwarzschild geometries enables us to distinguish charged and uncharged spacetimes by looking only at the orbital dynamics.

Misra, Vedant [Physics Department, Columbia University, New York, New York 10027 (United States); Levin, Janna [Department of Physics and Astronomy, Barnard College of Columbia University, 3009 Broadway, New York, New York 10027 (United States); Institute for Strings, Cosmology and Astroparticle Physics, Columbia University, New York, New York 10027 (United States)

2010-10-15

299

Analysing weak orbital signals in Gaia data  

NASA Astrophysics Data System (ADS)

Anomalous orbits are found when minimum-?2 estimation is applied to synthetic Gaia data for orbits with astrometric signatures comparable to the single-scan measurement error (Pourbaix 2002, A&A, 385, 686). These orbits are nearly parabolic, edge-on, and their major axes align with the line-of-sight to the observer. Such orbits violate the Copernican principle (CPr) and as such could be rejected. However, the preferred alternative is to develop a statistical technique that incorporates the CPr as a fundamental postulate. This can be achieved in a Bayesian context by defining a Copernican prior. Pourbaix's anomalous orbits then no longer arise. Instead, the selected orbits have a somewat higher ?2 but do not violate the CPr. The problem of detecting a weak additional orbit in an astrometric binary with a well-determined orbit is also treated.

Lucy, L. B.

2014-11-01

300

Orbiter CIU/IUS communications hardware evaluation  

NASA Technical Reports Server (NTRS)

Inertial Upper Stage (IUS) and DoD Communication Interface Unit (CIU) communication system design, hardware specifications, and interfaces were evaluated to determine their compatibility with the Orbiter payload communication and data handling equipment and the Orbiter network communication equipment.

Huth, G. K.

1979-01-01

301

Orbiter Kapton wire operational requirements and experience  

NASA Technical Reports Server (NTRS)

The agenda of this presentation includes the Orbiter wire selection requirements, the Orbiter wire usage, fabrication and test requirements, typical wiring installations, Kapton wire experience, NASA Kapton wire testing, summary, and backup data.

Peterson, R. V.

1994-01-01

302

NASA Now: Orbital Mechanics: Earth Observing Satellites  

NASA Video Gallery

This NASA Now program is all about satellites and their orbits. Dr. James Gleason, project scientist for NPP, explains what it takes for a satellite to stay in orbit, why there are different types ...

303

Two designs for an orbital transfer vehicle  

NASA Technical Reports Server (NTRS)

The Orbital Transfer Vehicle (OTV) and systems were researched in the following areas: avionics, crew systems, electrical power systems, environmental control/life support systems, navigation and orbital maneuvers, propulsion systems, reaction control systems (RCS), servicing systems, and structures.

Davis, Richard; Duquette, Miles; Fredrick, Rebecca; Schumacher, Daniel; Somers, Schaeffer; Stafira, Stanley; Williams, James; Zelinka, Mark

1988-01-01

304

#1 Stereo Orbit - Launch to Feb 2011  

NASA Video Gallery

The STEREO mission consists of two spacecraft orbiting the Sun, one moving a bit faster than Earth and the other a bit slower. In the time since the STEREO spacecraft entered these orbits near the ...

305

Management of ocular, orbital, and adnexal trauma  

SciTech Connect

This book contains 20 chapters. Some of the chapter titles are: The Ruptured Globe: Primary Care; Corneal Trauma, Endophthalmitis; Antibiotic Usage; Radiology of Orbital Trauma; Maxillofacial Fractures; Orbital Infections; and Basic Management of Soft Tissue Injury.

Spoor, T.C.; Nesi, F.A.

1988-01-01

306

Algorithms for orbit control on SPEAR  

SciTech Connect

A global orbit feedback system has been installed on SPEAR to help stabilize the position of the photon beams. The orbit control algorithms depend on either harmonic reconstruction of the orbit or eigenvector decomposition. The orbit motion is corrected by dipole corrector kicks determined from the inverse corrector-to-bpm response matrix. This paper outlines features of these control algorithms as applied to SPEAR.

Corbett, J.; Keeley, D.; Hettel, R.; Linscott, I.; Sebek, J. [Stanford Univ., CA (United States). Stanford Synchrotron Radiation Lab.

1994-06-01

307

Understanding pediatric bacterial preseptal and orbital cellulitis.  

PubMed

Pediatric preseptal and orbital cellulitis are infectious disorders that result in periorbital inflammation. Preseptal cellulitis is often associated with breaches in the skin barrier whereas orbital cellulitis is commonly associated with paranasal sinusitis. Orbital cellulitis may be associated with subperiosteal abscess. It is important to distinguish between preseptal from orbital cellulitis. Clinical examination and diagnostic imaging are useful in determining appropriate management. Patients are usually treated with broad spectrum antibiotics and surgery when indicated. PMID:20616919

Gonzalez, Mithra O; Durairaj, Vikram D

2010-04-01

308

Low thrust orbit determination program  

NASA Technical Reports Server (NTRS)

Logical flow and guidelines are provided for the construction of a low thrust orbit determination computer program. The program, tentatively called FRACAS (filter response analysis for continuously accelerating spacecraft), is capable of generating a reference low thrust trajectory, performing a linear covariance analysis of guidance and navigation processes, and analyzing trajectory nonlinearities in Monte Carlo fashion. The choice of trajectory, guidance and navigation models has been made after extensive literature surveys and investigation of previous software. A key part of program design relied upon experience gained in developing and using Martin Marietta Aerospace programs: TOPSEP (Targeting/Optimization for Solar Electric Propulsion), GODSEP (Guidance and Orbit Determination for SEP) and SIMSEP (Simulation of SEP).

Hong, P. E.; Shults, G. L.; Huling, K. R.; Ratliff, C. W.

1972-01-01

309

Of Orbits, Conics, and Grammar  

NASA Astrophysics Data System (ADS)

In the half-dozen or so years leading up to the publication of the Principia, Isaac Newton observed the comets of 1680 and 1682 and wrestled with the extent to which his law of gravitation could be applied. In time, he would see the connections between the four possible orbits of a satellite (circular, elliptical, parabolic, and hyperbolic) and the four curves produced by the careful carving of a cone. But if we look a little further into the conic sections, we find some interesting connections among the natural orbit of a satellite, ancient mathematics, and the roots of familiar words. Illuminating these connections for introductory physics students may help them to better understand the role of language and mathematics in the descriptions of science.

Henderson, Hugh

2005-02-01

310

On-orbit spacecraft reliability  

NASA Technical Reports Server (NTRS)

Operational and historic data for 350 spacecraft from 52 U.S. space programs were analyzed for on-orbit reliability. Failure rates estimates are made for on-orbit operation of spacecraft subsystems, components, and piece parts, as well as estimates of failure probability for the same elements during launch. Confidence intervals for both parameters are also given. The results indicate that: (1) the success of spacecraft operation is only slightly affected by most reported incidents of anomalous behavior; (2) the occurrence of the majority of anomalous incidents could have been prevented piror to launch; (3) no detrimental effect of spacecraft dormancy is evident; (4) cycled components in general are not demonstrably less reliable than uncycled components; and (5) application of product assurance elements is conductive to spacecraft success.

Bloomquist, C.; Demars, D.; Graham, W.; Henmi, P.

1978-01-01

311

Polarization from an orbiting spot  

NASA Astrophysics Data System (ADS)

The polarization from a spot orbiting around Schwarzschild and extreme Kerr black holes is studied. We assume different models of local polarization. Firstly, as a toy model we set local polarization vector either normal to the disc plane, or we assume strictly azimuthal direction. Then we examine more realistic situation with a spot arising due to the emission from the primary source above the disc. We employ either Rayleigh single scattering or Compton multiple scattering approximations. Overall flux, degree and angle of polarization integrated over the whole orbit as well as their time dependence during the spot revolution are examined as functions of the observer's inclination angle. The gravitational and Doppler shifts, lensing effect as well as time delays are taken into account.

Dov?iak, Michal; Karas, Vladimír; Matt, Giorgio

2007-04-01

312

The Mercury Dual Orbiter mission  

NASA Technical Reports Server (NTRS)

The Mercury Orbiter (MeO) will carry out a full range of particles, fields, and planetary imaging science at Mercury. Present mission plans call for a launch in 1999 with a flight time of about 4.5 years. By means of multiple Venus and Mercury gravitational assists, the mission can be accomplished with present U.S. launch vehicles and a very large payload can be placed in orbit around Mercury. The dual-spacecraft concept will permit outstanding scientific study of solar cosmic rays and the solar wind throughout the inner heliosphere from 0.3 AU to 1.0 AU. Modest enhancements to the planned magnetospheric instruments and utilization of onboard solar instruments will permit unique investigation of solar particle acceleration and transport with the MeO spacecraft.

Baker, D. N.; Slavin, J. A.

1990-01-01

313

Lunar Orbiter: Moon and Earth  

NASA Technical Reports Server (NTRS)

The worlds first view of the Earth taken by a spacecraft from the vicinity of the Moon. The photo was transmitted to Earth by the United States Lunar Orbiter I and recieved at the NASA tracking station at Robledo de Chavela near Madrid, Spain. This crescent of the Earth was photographed August 23 at 16:35 GMT when the spacecraft was on its 16th orbit and just about to pass behind the Moon. This is the view the astronauts will have when they come around the backside of the Moon and face the Earth. The Earth is shown on the left of the photo with the U.S. east coast in the upper left, southern Europe toward the dark or night side of the Earth, and Antartica at the bottom of the Earth crescent. The surface of the Moon is shown on the right side of the photograph.

1966-01-01

314

The Orbiting Primate Experiment (OPE)  

NASA Technical Reports Server (NTRS)

Instrumentation and life support systems are described for an experiment to determine the physiological effects of long term space flight on unrestrained, minimally instrumented rhesus macaques flown in orbit for periods up to six months or one year. On return from orbit, vestibular, cardiovascular, and skeletal muscle function will be tested. Blood chemistry and hematological studies will be conducted as well as tests of the immunological competence of selected animals. Nasal, rectal, and throat swabs will be used for bacterial and viral studies, and histopathological and histochemical investigations will be be made of all organs using light and electron microscopy. The experiment is being considered as a payload for the biomedical experiment scientific satellite.

Bourne, G. H.; Debourne, M. N. G.; Mcclure, H. M.

1977-01-01

315

The Orbital Workshop Sleep Compartment  

NASA Technical Reports Server (NTRS)

This wide-angle view is of the Orbital Workshop (OWS) sleep compartment, located in the lower level of the OWS. Each crewman was assigned a small space for sleeping and zipped themselves into sleeping bags stretched against the wall. Because of the absence of gravity, sleeping comfort was achieved in any position relative to the spacecraft; body support was not necessary. Sleeping could be accommodated quite comfortably in a bag that held the body at a given place in Skylab.

1972-01-01

316

Assembling the Skylab Orbital Workshop  

NASA Technical Reports Server (NTRS)

This photograph was taken during assembly of the bottom and upper floors of the Skylab Orbital Workshop (OWS). The OWS was divided into two major compartments. The lower level provided crew accommodations for sleeping, food preparation and consumption, hygiene, waste processing and disposal, and performance of certain experiments. The upper level consisted of a large work area and housed water storage tanks, a food freezer, storage vaults for film, scientific airlocks, mobility and stability experiment equipment, and other experimental equipment.

1970-01-01

317

Opportunity Tracks Seen from Orbit  

NASA Technical Reports Server (NTRS)

[figure removed for brevity, see original site] Figure 1

NASA's Mars Exploration Rover Opportunity landed on the red planet a year ago. This enhanced-resolution image from the Mars Orbiter Camera on NASA's Mars Global Surveyor orbiter is the only picture obtained thus far (by Jan. 24, 2005) that shows the tracks made by Opportunity.

The image was acquired on April 26, 2004, during Opportunity's 91st martian day, or sol. That was the first day of Opportunity's extended mission, and the rover had recently completed exploration of small 'Fram Crater' on the route from its landing site toward 'Endurance Crater,' where it would eventually spend six months. The rover itself can be seen in this image -- an amazing accomplishment, considering that the orbiter was nearly 400 kilometers (nearly 250 miles) away at the time! Also visible and labeled on this image are the spacecraft's lander, backshell, parachute and heat shield, plus effects of its landing rockets.

The camera captured this image with use of a technique called compensated pitch and roll targeted observation. In this method, the entire spacecraft rolls as it passes over the target area so the camera can scan in a way that sees details at three times higher resolution than the camera's normal high-resolution capability.

The tracks made by Opportunity on the sandy surface of Meridiani Planum are not quite as visible from orbit as are the tracks made in Gusev Crater by the other Mars Exploration Rover, Spirit. A dustier surface at the Spirit site increases contrast between the tracks and the surrounding surfaces. Indeed, some parts of the track made by Opportunity are not visible in this image. Sunlight illuminates the scene from the left. North is toward the top of the image. The 100-meter scale bar is 109 yards long.

2005-01-01

318

Ancient schwannoma of the orbit.  

PubMed

The ancient schwannoma is a rare variant of a neurilemoma with a course typical of a slow-growing benign neoplasm. Histologically, it can be confused with a malignant mesenchymal tumor because of increased cellularity, nuclear pleomorphism, and hyperchromatism. Despite the degree of nuclear atypia, mitotic figures are absent. We describe the clinical and histopathologic features of an ancient schwannoma of the orbit. A need for early removal of such tumors is recommended to prevent complications. PMID:25136229

Kulkarni, Anjali S; Anjum, Shaziya; Kokandakar, Hemant R; Bindu, Rajan S; Awargaonkar, Amarnath

2014-05-01

319

Vigilance problems in orbiter processing  

NASA Technical Reports Server (NTRS)

A pilot experiment was done to determine what factors influence potential performance errors related to vigilance in Orbiter processing activities. The selected activities include post flight inspection for burned gap filler material and pre-rollout inspection for tile processing shim material. It was determined that the primary factors related to performance decrement were the color of the target and the difficulty of the target presentation.

Swart, William W.; Safford, Robert R.; Kennedy, David B.; Yadi, Bert A.; Barth, Timothy S.

1993-01-01

320

Mars Orbiting Plasma Surveyor (MOPS)  

NASA Astrophysics Data System (ADS)

Mars Orbiting Plasma Surveyor (MOPS) S. Barabash (1), M. André (2), L. G. Blomberg (3), R. Lundin (1),G. T. Marklund (3), P. Rathsman (4), F. von Schéele (4), J.-E. Wahlund (2) (1) Swedish Institute of Space Physics, Kiruna, Sweden (stas@irf.se) (2) Swedish Institute of Space Physics, Uppsala, Sweden (3) Royal Institute of Technology, Department of Space and Plasma Physics , Stockholm, Sweden (4) Swedish Space Corporation, Solna, Sweden Mars Orbiting Plasma Surveyor (MOPS) is a microsatellite mission focused on studies of the near - Mars environment and the planet - solar wind interaction. The recent findings by the ESA Mars Express mission further highlighted the complexity of the processes taking place at the planet resulting from the solar wind interaction that strongly affect the planet's atmosphere. However, despite many previous Martian missions carrying different types of space plasma experiments, a comprehensive investigation including simultaneous measurements of particles, fields, and waves has never been performed. We propose a spinning spacecraft of a mass of 50-80 kg with a 10 kg payload which can "hitchhike" on another platform until Mars orbit insertion and then be released into a suitable orbit. The spacecraft design is based on the experience gained in very successful Swedish space plasma missions, Viking, Freja, Astrid -1, and Astrid - 2. In the present mission design, the MOPS spacecraft is equipped with its own 1m high gain antenna for direct communication with the Earth. The payload includes a wave experiment with wire booms, magnetometer with a rigid boom, electron and ion energy spectrometers and an ion mass analyser. An energetic neutral atom imager and an UV photometer may complete the core payload.

Barabash, S.; Andre, M.; Blomberg, L. G.; Lundin, R.; Marklund, G. T.; Rathsman, P.; von Scheele, F.; Wahlund, J.-E.

321

Viking orbiter system primary mission  

NASA Technical Reports Server (NTRS)

An overview of Viking Orbiter (VO) system and subsystem performances during the primary mission (the time period from VO-1 launch on August 20, 1975, through November 15, 1976) is presented. Brief descriptions, key design requirements, pertinent historical information, unique applications or situations, and predicted versus actual performances are included for all VO-1 and VO-2 subsystems, both individually and as an integrated system.

Goudy, J. R.

1977-01-01

322

Moving the Mars Reconnaissance Orbiter  

NASA Technical Reports Server (NTRS)

In late October 2004, NASA's Mars Reconnaissance Orbiter was moved from the High Bay 100,000-class clean room at Lockheed Martin Space Systems, Denver, to the facility's Reverberant Acoustic Lab, where system environmental testing will continue through March 2005. Shown here are technicians guiding the spacecraft as it is lowered onto its transporter interface ring prior to installation of the shipping-container lid.

2005-01-01

323

Ancient schwannoma of the orbit  

PubMed Central

The ancient schwannoma is a rare variant of a neurilemoma with a course typical of a slow-growing benign neoplasm. Histologically, it can be confused with a malignant mesenchymal tumor because of increased cellularity, nuclear pleomorphism, and hyperchromatism. Despite the degree of nuclear atypia, mitotic figures are absent. We describe the clinical and histopathologic features of an ancient schwannoma of the orbit. A need for early removal of such tumors is recommended to prevent complications. PMID:25136229

Kulkarni, Anjali S.; Anjum, Shaziya; Kokandakar, Hemant R.; Bindu, Rajan S.; Awargaonkar, Amarnath

2014-01-01

324

Remote orbital servicing system concept  

NASA Technical Reports Server (NTRS)

Increased applications of automation technology identified as necessary for NASA to carry out its missions within the constraints of future funding and available physical resources are described. A concept for a Remote Orbital Servicing System (ROSS) based on present teleoperator and robotics technology is presented. A single servicer design compatible with three specified spacecraft, capable of performing service to the same extent as manned extravehicular activity, controlled from a ground control station, and using currently available technology is conceptualized.

Meintel, A. J.; Schappell, R. T.

1982-01-01

325

The Mercury dual orbiter mission  

Microsoft Academic Search

The Mercury Orbiter (MeO) will carry out a full range of particles, fields, and planetary imaging science at Mercury. Present mission plans call for a launch in 1999 with a flight time of about 4.5 years. By means of multiple Venus and Mercury gravitational assists, the mission can be accomplished with present U.S. launch vehicles and a very large payload

D. N. Baker; J. A. Slavin

1990-01-01

326

A Mercury orbiter mission design  

Microsoft Academic Search

The paper presents the results of the first stage of a Mercury Orbiter Mission Concept Definition study originated by NASA, with emphasis on a proposed end-to-end mission scenario. The science rationale and the strawman payload are presented, along with the spacecraft design based on a novel use of conventional technology that eliminates the need for high-cost high-risk technology development. A

Chen-Wan L. Yen; David H. Collins; Scott A. Meyer

1989-01-01

327

Some Observations on Molecular Orbital Theory  

ERIC Educational Resources Information Center

A few flawed predictions in the context of homonuclear diatomic molecules are presented in order to introduce students to molecular orbital (MO) theory. A common misrepresentation of the relationship between the energy of an atomic orbital and the energy of the MO associated with the atomic orbital is illustrated.

Journal of Chemical Education, 2005

2005-01-01

328

Orbital exenteration for invasive skin tumours  

Microsoft Academic Search

Orbital exenteration aims at local control of disease invading the orbit that is potentially fatal or relentlessly progressive. Of all exenterations presenting to ophthalmologists, 40–50% are required for tumours in the eyelid or periocular skin. 99% of these are basal cell carcinomas and 4–6% each are squamous cell carcinomas or sebaceous gland carcinomas. Orbital invasion results in progressive fixation of

A G Tyers

2006-01-01

329

Double lunar swing-by orbits revisited  

NASA Astrophysics Data System (ADS)

The double lunar swing-by orbits are a special kind of orbits in the Earth-Moon system. These orbits repeatedly pass through the vicinity of the Moon and change their shapes due to the Moon's gravity. In the synodic frame of the circular restricted three-body problem consisting of the Earth and the Moon, these orbits are periodic, with two close approaches to the Moon in every orbit period. In this paper, these orbits are revisited. It is found that these orbits belong to the symmetric horseshoe periodic families which bifurcate from the planar Lyapunov family around the collinear libration point L3. Usually, the double lunar swing-by orbits have k= i+ j loops, where i is the number of the inner loops and j is the number of outer loops. The genealogy of these orbits with different i and j is studied in this paper. That is, how these double lunar swing-by orbits are organized in the symmetric horseshoe periodic families is explored. In addition, the 2 n lunar swing-by orbits ( n?2) with 2 n close approaches to the Moon in one orbit period are also studied.

Hou, XiYun; Liu, Lin

2014-04-01

330

A Southern Hemisphere radar meteor orbit survey  

Microsoft Academic Search

A meteor radar system has been operated on a routine basis near Christchurch, New Zealand, to determine the orbits of Earth-impacting interplanetary dust and meteoroids. The system sensitivity is +13 visual magnitude, corresponding to approximately 100 micron sized meteoroids. With an orbital precision of 2 degrees in angular elements and 10 percent in orbital energy (1\\/a), the operation yields an

W. Jack Baggaley; Duncan I. Steel; Andrew D. Taylor

1992-01-01

331

Current Status of Venus orbiter Akatsuki  

E-print Network

Current Status of Venus orbiter Akatsuki Takeshi Imamura (JAXA, Japan) and AKATSUKI Project Team #12;Venus orbiter Akatsuki ·! Science target : `Weather of Venus' ­! Mechanism of `super was launched in May 2010. The Venus orbit insertion scheduled for December 2010 has failed. Now Akatsuki

Widemann, Thomas

332

The Meaning of d-Orbital Labels  

ERIC Educational Resources Information Center

The orbital labels when considered as the angular part of the wavefunction can serve as an inclusive principle, which the students can use to construct the spatial shapes of the d orbitals from their labels. The spatial orientation of the different d orbitals guides the crystal field theory which includes d(sub xy), d(sub yz) and d(sub xz) lying…

Ashkenazi, Guy

2005-01-01

333

An ion propulsion orbit manoeuvring vehicle  

Microsoft Academic Search

It is shown that the concept of a reusable ion propulsion orbit maneuvering vehicle (OMV) can fulfill two particular orbital dynamics needs for the coming decades. On is the boosting of nonoperational satellites out of GEO in order to reduce GEO crowding and frequency transmission crosstalk. The other is the ability to maneuver certain satellites and other orbital debris out

R. Holdaway; M. Flaherty

1990-01-01

334

Orbit determination for ISRO satellite missions  

Microsoft Academic Search

Indian Space Research Organisation (ISRO) has been successful in using the in-house developed orbit determination and prediction software for satellite missions of Bhaskara, Rohini and APPLE. Considering the requirements of satellite missions, software packages are developed, tested and their accuracies are assessed. Orbit determination packages developed are SOIP, for low earth orbits of Bhaskara and Rohini missions, ORIGIN and ODPM,

Ch. Sreehari Rao; S. K. Sinha

1985-01-01

335

Project Management in NASA Mars Climate Orbiter  

E-print Network

Report on Project Management in NASA by the Mars Climate Orbiter Mishap Investigation Board March Acknowledgements 5 Executive Summary 6 1. Introduction 10 2. The Mars Climate Orbiter Mission: Observations Boards 44 7. Concluding Remarks 47 Appendixes A. Letter Establishing the Mars Climate Orbiter Mishap

Rhoads, James

336

Localized correlation treatment using natural bond orbitals  

Microsoft Academic Search

We present studies using natural bond orbitals (NBOs) as a starting point for a localized electron correlation treatment, as these kind of localized orbitals lead to CCSD results which show significant transferability and exponential decay patterns in the T?2 amplitudes. The NBO CCSD approach combines the advantages of both the HF CCSD formulation (less amplitudes, orthogonal orbitals) and the AO-based

N. Flocke; Rodney J. Bartlett

2003-01-01

337

STATISTICAL ANALYSIS OF A DETERMINISTIC STOCHASTIC ORBIT  

SciTech Connect

If the solution of a deterministic equation is stochastic (in the sense of orbital instability), it can be subjected to a statistical analysis. This is illustrated for a coded orbit of the Chirikov mapping. Statistical dependence and the Markov assumption are tested. The Kolmogorov-Sinai entropy is related to the probability distribution for the orbit.

Kaufman, Allan N.; Abarbanel, Henry D.I.; Grebogi, Celso

1980-05-01

338

New concepts for Mercury orbiter missions  

Microsoft Academic Search

The next logical step in the exploration of Mercury is an orbiter mission. A conflict exists between those in the field of planetary sciences who desire a mission with a low circular orbit, and scientists in the fields and particles disciplines, who generally prefer a highly elliptical spacecraft orbit. The thermal environment imposed by the sun and planet render the

J. R. French; J. R. Stuart; B. Zeldin

1978-01-01

339

Frozen orbit analysis in the Martian system  

Microsoft Academic Search

A frozen orbit is an orbit whose time rate of change of the argument of the periapsis, the eccentricity, the semi major axis, or the angle of inclination (i) is approximately equal to zero. Martian frozen orbits are known to exist for polar trajectories with altitudes from 300 km to 1000 km. The objective of this study was to determine

James W. Foister III

1987-01-01

340

Conversion Between Osculating and Mean Orbital Elements  

NASA Technical Reports Server (NTRS)

Osculating/Mean Orbital Element Conversion (C version) (OSMEANC) is a C-language computer program that performs precise conversions between osculating and mean classical orbital elements. OSMEANC can be used for precise design of spacecraft missions and maneuvers and precise calculation of planetary orbits. The program accounts for the full complexity of gravitational fields, including aspherical and third-body effects.

Guinn, Joseph; Chung, Min-Kun; Vincent, Mark

2006-01-01

341

Orbital Space Plane (OSP) Program  

NASA Technical Reports Server (NTRS)

Lockheed Martin has been an active participant in NASA's Space Launch Initiative (SLI) programs over the past several years. SLI, part of NASA's Integrated Space Transportation Plan (ISTP), was restructured in November of 2002 to focus the overall theme of safer, more afford-able space transportation along two paths - the Orbital Space Plane Program and the Next Generation Launch Technology programs. The Orbital Space Plane Program has the goal of providing rescue capability from the International Space Station by 2008 and transfer capability for crew (and limited cargo) by 2012. The Next Generation Launch Technology program is combining research and development efforts from the 2nd Generation Reusable Launch Vehicle (2GRLV) program with cutting-edge, advanced space transportation programs (previously designated 3rd Generation) into one program aimed at enabling safe, reliable, cost-effective reusable launch systems by the middle of the next decade. Lockheed Martin is one of three prime contractors working to bring Orbital Space Plane system concepts to a system definition level of maturity by December of 2003. This paper and presentation will update the international community on the progress of the' OSP program, from an industry perspective, and provide insights into Lockheed Martin's role in enabling the vision of a safer, more affordable means of taking people to and from space.

McKenzie, Patrick M.

2003-01-01

342

Extended Duration Orbiter Medical Project  

NASA Technical Reports Server (NTRS)

The Extended Duration Orbiter (EDO) program addresses a need for more time to perform experiments and other tasks during Space Shuttle missions. As a part of this program, the Extended Duration Orbiter Medical Project (EDOMP) has been instituted to obtain information about physiologic effects of extending mission duration and the effectiveness of countermeasures against factors that might compromise crew health, safety, or performance on extended-duration missions. Only those investigations that address and characterize operational problems, develop countermeasures, or evaluate the effectiveness of countermeasures will be pursued. The EDOMP investigations will include flight-associated Detailed Supplementary Objectives as well as ground-based studies simulating the influence of microgravity. Investigator teams have been formed in the following areas: biomedical physiology, cardiovascular and fluid/electrolyte physiology, environmental health, muscle and exercise physiology, and neurophysiology. Major operational questions must be answered in each of these areas, and investigations have been designed to answer them. The EDO program will proceed only after countermeasures have been shown to be effective in preventing or mitigating the adverse changes they have been designed to attenuate. The program is underway and will continue on each Shuttle flight as the manifest builds toward a 16-day orbital flight.

Leach, C. S.; Pool, S. L.; Sawin, C. F.; Nicogossian, A. E.

1990-01-01

343

Fitting orbits to tidal streams  

E-print Network

Recent years have seen the discovery of many tidal streams through the Galaxy. Relatively straightforward observations of a stream allow one to deduce three phase-space coordinates of an orbit. An algorithm is presented that reconstructs the missing phase-space coordinates from these data. The reconstruction starts from assumed values of the Galactic potential and a distance to one point on the orbit, but with noise-free data the condition that energy be conserved on the orbit enables one to reject incorrect assumptions. The performance of the algorithm is investigated when errors are added to the input data that are comparable to those in published data for the streams of Pal 5. It is found that the algorithm returns distances and proper motions that are accurate to of order one percent, and enables one to reject quite reasonable but incorrect trial potentials. In practical applications it will be important to minimize errors in the input data, and there is considerable scope for doing this.

James Binney

2008-02-11

344

Synchronous orbit power technology needs  

NASA Technical Reports Server (NTRS)

The needs are defined for future geosynchronous orbit spacecraft power subsystem components, including power generation, energy storage, and power processing. A review of the rapid expansion of the satellite communications field provides a basis for projection into the future. Three projected models, a mission model, an orbit transfer vehicle model, and a mass model for power subsystem components are used to define power requirements and mass limitations for future spacecraft. Based upon these three models, the power subsystems for a 10 kw, 10 year life, dedicated spacecraft and for a 20 kw, 20 year life, multi-mission platform are analyzed in further detail to establish power density requirements for the generation, storage and processing components of power subsystems as related to orbit transfer vehicle capabilities. Comparison of these requirements to state of the art design values shows that major improvements, by a factor of 2 or more, are needed to accomplish the near term missions. However, with the advent of large transfer vehicles, these requirements are significantly reduced, leaving the long lifetime requirement, associated with reliability and/or refurbishment, as the primary development need. A few technology advances, currently under development, are noted with regard to their impacts on future capability.

Slifer, L. W., Jr.; Billerbeck, W. J.

1979-01-01

345

Ejs Quartic Potential Orbit Model  

NSDL National Science Digital Library

The Ejs Quartic Potential Orbit model displays the dynamics of a mass orbiting a much larger mass subject to a quartic potential, C/râ´. The simulation displays the motion of the smaller mass and the effective potential energy diagram. The initial energy of the system can be changed via textbox and the initial conditions can also be changed by dragging the mass or dragging the pink circle in the effect potential energy diagram. You can modify this simulation if you have Ejs installed by right-clicking within the plot and selecting âOpen Ejs Modelâ from the pop-up menu item. Ejs Quartic Potential Orbit model was created using the Easy Java Simulations (Ejs) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_ehu_central_forces_quarticpotential.jar file will run the program if Java is installed. Ejs is a part of the Open Source Physics Project and is designed to make it easier to access, modify, and generate computer models. Additional Ejs models for Newtonian mechanics are available. They can be found by searching ComPADRE for Open Source Physics, OSP, or Ejs.

Aguirregabiria, Juan

2008-08-18

346

Mutual Orbits of Transneptunian Binaries  

NASA Astrophysics Data System (ADS)

We report the latest results from a program of high spatial resolution imaging to resolve the individual components of binary transneptunian objects. These observations use Hubble Space Telescope and also laser guide star adaptive optics systems on Keck and Gemini telescopes on Mauna Kea. From relative astrometry over multiple epochs, we determine the mutual orbits of the components, and thus the total masses of the systems. Accurate masses anchor subsequent detailed investigations into the physical characteristics of these systems. For instance, dynamical masses enable computation of bulk densities for systems where the component sizes can be estimated from other measurements. Additionally, patterns in the ensemble characteristics of binary orbits offer clues to circumstances in the protoplanetary nebula when these systems formed, as well as carrying imprints of various subsequent dynamical evolution processes. The growing ensemble of known orbits shows intriguing patterns that can shed light on the evolution of this population of distant objects. This work has been supported by an NSF Planetary Astronomy grant and by several Hubble Space Telescope and NASA Keck data analysis grants. The research makes use of data from the Gemini Observatory obtained through NOAO survey program 11A-0017, from a large number of Hubble Space Telescope programs, and from several NASA Keck programs.

Grundy, William M.; Noll, K. S.; Roe, H. G.; Porter, S. B.; Trujillo, C. A.; Benecchi, S. D.; Buie, M. W.

2012-10-01

347

Free-fall orbits and heteroclinic orbits to triple collisions, and shadowing in the isosceles  

E-print Network

RIMS-1672 Free-fall orbits and heteroclinic orbits to triple collisions, and shadowing KYOTO UNIVERSITY, Kyoto, Japan #12;Free-fall orbits and heteroclinic orbits to triple collisions, and shadowing in the isosceles three-body problem Mitsuru Shibayama May 15, 2009 Abstract We investigate free-fall

348

GOCE Gravity Gradients in an Orbital Aspect  

NASA Astrophysics Data System (ADS)

This work includes a study of the possibility of the Gravity Field and Steady-State Ocean Circulation Explorer Mission (GOCE) satellite orbit improvement using gravity gradient observations. The orbit improvement is performed by a dedicated software package, called Orbital Computation System (OCS), which is based on the classical least squares method. In an iterative process, the corrections to the initial state vector components of the satellite are estimated, using dynamical models describing gravitational perturbations. An important component implemented in the OCS package is the Cowell 8th order numerical integration procedure, which directly generates the satellite orbit. Taking into account the GOCE real and simulated gravity gradients, different variants of solution of the orbit improvement process were obtained. The improved orbits were compared to the GOCE reference orbits (Precise Science Orbits of the GOCE satellite delivered by the European Space Agency) using the root mean squares (RMS) of the differences between the satellite positions on the improved orbits and on the reference ones. The comparison between the improved orbits and the reference ones was performed with respect to the inertial reference frame (IRF) at J2000.0 epoch. RMS values for the solutions based on the real gravity gradients measurements are at a level of hundreds of kilometers and more. This means that the orbit improvement using the real gravity gradients is ineffective. However, all solutions using the simulated gravity gradients, have RMS values below the threshold determined by RMS values for the computed orbits (without the improvement). The most promising results have been achieved here in the case of improving of short orbital arcs with the lengths from a few to tens of minutes. For these short arcs, RMS values reach the level of centimeters, which is close to the accuracy of Precise Science Orbit of GOCE satellite. Additional research have provided requirements for the effective orbit improvement in terms of the accuracy and spectral content of measured gravity gradients.

Bobojc, Andrzej; Drozyner, Andrzej

2014-05-01

349

Understanding glycine conformation through molecular orbitals  

NASA Astrophysics Data System (ADS)

The four most stable Cs conformers of glycine have been investigated using a variety of quantum-mechanical methods based on Hartree-Fock theory, density-functional theory (B3LYP and statistical average of orbital potential), and electron propagation (OVGF) treatments. Information obtained from these models were analyzed in coordinate and momentum spaces using dual space analysis to provide insight based on orbitals into the bonding mechanisms of glycine conformers, which are generated by rotation of C-O(H) (II), C-C (III), and C-N (IV) bonds from the global minimum structure (I). Wave functions generated from the B3LYP/TZVP model revealed that each rotation produced a unique set of fingerprint orbitals that correspond to a specific group of outer valence orbitals, generally of a' symmetry. Orbitals 14a', 13a', 12a', and 11a' are identified as the fingerprint orbitals for the C-O(H) (II) rotation, whereas fingerprint orbitals for the C-C (III) bond rotation are located as 16a' [highest occupied molecular orbital (HOMO)], 15a' [next highest molecular occupied molecular orbital (NHOMO)], 14a', and 12a' orbitals. Fingerprint orbitals for IV generated by the combined rotations around the C-C, C-O(H), and C-N bonds are found as 16a', 15a', 14a', 13a', and 11a', as well as in orbitals 2a'' and 1a''. Orbital 14a' is identified as the fingerprint orbital for all three conformational processes, as it is the only orbital in the outer valence region which is significantly affected by the conformational processes regardless rotation of which bond. Binding energies, molecular geometries, and other molecular properties such as dipole moments calculated based on the specified treatments agree well with available experimental measurements and with previous theoretical calculation.

Falzon, Chantal T.; Wang, Feng

2005-12-01

350

Analysis of Relativistic Stellar Aberration for the Space Interferometry Mission  

Microsoft Academic Search

We present results of our recent study of the issue of relativistic stellar aberration requirements for SIM in Earth-trailing orbit. In particular, we estimated the astrometric errors introduced by imperfect metrology, errors in baseline length estimations, and those due to the relativistic orbital motion. We have shown that motion of the spacecraft in the direction perpendicular to a tile of

S. G. Turyshev

1999-01-01

351

ExoMars/TGO Science Orbit Design  

NASA Technical Reports Server (NTRS)

This paper describes the development of the science orbit for the 2016 ESA/NASA collaborative ExoMars/Trace Gas Orbiter (TGO) mission. The initial requirements for the ExoMars/TGO mission simply described the science orbit as circular with a 400 km altitude and a 74 deg inclination. Over the past year, the JPL mission design team worked with the TGO science teams to refine the science orbit requirements and recommend an orbit that would be operationally feasible, easy to maintain, and most important allow the science teams to best meet their objectives.

Long, Stacia; Lyons, Dan; Guinn, Joe; Lock, Rob

2012-01-01

352

Payload/orbiter contamination control requirement study  

NASA Technical Reports Server (NTRS)

A study was conducted to determine and quantify the expected particulate and molecular on-orbit contaminant environment for selected space shuttle payloads as a result of major shuttle orbiter contamination sources. Individual payload susceptibilities to contamination are reviewed. The risk of payload degradation is identified and preliminary recommendations are provided concerning the limiting factors which may depend on operational activities associated with the payload/orbiter interface or upon independent payload functional activities. A basic computer model of the space shuttle orbiter which includes a representative payload configuration is developed. The major orbiter contamination sources, locations, and flux characteristics based upon available data have been defined and modeled.

Bareiss, L. E.; Rantanen, R. O.; Ress, E. B.

1974-01-01

353

Performance aerodynamics of aeroassisted orbital transfer vehicles  

NASA Technical Reports Server (NTRS)

A method for predicting the performance aerodynamics of aeroassisted orbital transfer vehicles was developed based on techniques that were used in the aerodynamic databook of the Space Shuttle orbiter and theories from the Hypersonic Arbitrary Body Program. The method spans the entire flight profile of the aeroassisted orbital transfer vehicles from the extreme high altitude non-continuum regime to the highly viscous continuum regime. Results from this method are compared with flight data from the Shuttle orbiter, Apollo Capsule, and the Viking Aeroshell. Finally, performance aerodynamics are estimated for three aeroassisted orbital transfer vehicles that range from low to high lift-to-drag ratio configurations.

Wilhite, A. W.; Arrington, J. P.; Mccandless, R. S.

1984-01-01

354

On-orbit flight control algorithm description  

NASA Technical Reports Server (NTRS)

Algorithms are presented for rotational and translational control of the space shuttle orbiter in the orbital mission phases, which are external tank separation, orbit insertion, on-orbit and de-orbit. The program provides a versatile control system structure while maintaining uniform communications with other programs, sensors, and control effectors by using an executive routine/functional subroutine format. Software functional requirements are described using block diagrams where feasible, and input--output tables, and the software implementation of each function is presented in equations and structured flow charts. Included are a glossary of all symbols used to define the requirements, and an appendix of supportive material.

1975-01-01

355

Frozen orbit analysis in the Martian system  

NASA Astrophysics Data System (ADS)

A frozen orbit is an orbit whose time rate of change of the argument of the periapsis, the eccentricity, the semi major axis, or the angle of inclination (i) is approximately equal to zero. Martian frozen orbits are known to exist for polar trajectories with altitudes from 300 km to 1000 km. The objective of this study was to determine if other regions with characteristics similar to the known frozen orbits exist, taking into account the perturbative effects due to a 6 x 6 gravity field and atmospheric drag. First, the geopotential equation was derived for both spherical coordinates and the classical orbital elements. Next, a model for the atmospheric drag was developed. Using these two models, a FORTRAN computer model named ASAP (Artificial Satellite Analysis Program) was analyzed for accuracy. This program proved to be highly reliable, and was used to carry out further analysis. Two of the three trajectories planned for the future Mars Geoscience/Climatology Orbiter (MGCO) are frozen orbits. In order to determine the characteristics of w, e, a, and i of a frozen orbit, one of the MGCO frozen orbits was examined in both a 6 x 0 and a 6 x 6 gravity field. The analysis showed that the above orbital elements are not periodic over one orbital period (when in the presence of a 6 x 6 gravity field), but they are bounded over one axial period.

Foister, James W., III

1987-12-01

356

Localized and Spectroscopic Orbitals: Squirrel Ears on Water.  

ERIC Educational Resources Information Center

Reexamines the electronic structure of water considering divergent views. Discusses several aspects of molecular orbital theory using spectroscopic molecular orbitals and localized molecular orbitals. Gives examples for determining lowest energy spectroscopic orbitals. (ML)

Martin, R. Bruce

1988-01-01

357

Orbital perturbations of low orbiters in a dusty Martian atmosphere  

NASA Astrophysics Data System (ADS)

A study of a low-orbit polar satellite around Mars is carried out using Lagrangian mechanics principles and Lagrange's planetary equations in which both conservative and non-conservative forces are modelled. Our work differs from state-of-the-art Newtonian and Gaussian methods and enhances the modelling of the perturbing potentials arising from areopotential anomalies: atmospheric drag, dust drag, solar radiation pressure, relativistic effects, third-body, and solid-body tides on Mars. Because we are interested in analytical/numerical expressions and results, the Lagrangian method constitutes a more suitable analytical approach than does the traditional Gaussian. The resulting system of equations of motion for the satellite provides the time derivatives of the orbital elements as functions of the gravitational harmonic coefficients and all the perturbing effects we considered. When the time derivatives of the orbital elements are available from satellite tracking observations, the equations can be used in a least-squares estimation process to provide, the gravitational field in terms of harmonic coefficients. To understand the utility of the derived equations of motion, we obtain analytical expressions for the gravitational harmonics of degree and order six. These expressions involve, among other variables, the inclination and eccentricity functions and their time derivatives. In particular, the numerical calculation of high-degree/order eccentricity and inclination functions are known to be numerically unstable. To remove such instabilities, we use an effective and efficient transformation that relates the eccentricity functions to Hansen coefficients, using Bessel functions of the first kind. Similarly, the inclination functions are transformed into hypergeometric series. Analytical and numerical tests show that the transformed inclination and eccentricity functions are remarkably stable up to degree/order eighty. This is very important when the Lagrangian method is used to determine the gravitational field with high accuracy and spatial resolution. We study the effects of atmospheric dust on low orbiters by considering a low velocity "fluid" dust medium containing dust particles of radius 1.25 mum, by deriving a velocity-cube dissipation function that represents the energy density dissipated by the satellite per unit time. We have developed a method for determining a satellite's dust drag coefficient provided that its geometrical shape is known. For example, for a cylindrical satellite, we find that Cd = 4. We also calculate an upper bound to the atmospheric dust density of 8.323 x 10-10 kg m-3 at an altitude of 100 km. Local dust storm-clouds in the range of 800 - 1000 km reduce the semi-major axis from a few centimetres up to a few decimetres per day. Similarly, episodic dust clouds of 10 km in length and at low altitudes (65 - 90 km) result in sub-millimetre per day losses in the semi-major axis. The satellite's mass increase due to dust adhesion is modelled by considering the dust as an aerosol moving in an atmospheric fluid. Adhesion affects the semi-major axis by a few millimetres to a few decimetres per year. Other orbital elements are affected only by insignificant amounts.

Haranas, Ioannis Iraklis

2010-12-01

358

Orbital blowout fractures in sport.  

PubMed

One-third of orbital blowout fractures are sustained during sport. Soccer is most commonly involved. Though visual acuity recovery is usually complete, permanent loss of binocular visual field is almost universal. Typically high-energy blows by opponent's finger, fist, elbow, knee or boot are responsible. Injuries to the eye itself may also be sustained and should be looked for. Ocular protection may be feasible in some sports, but the main preventive measure to be addressed is the reduction in aggressive play or deliberate injury. PMID:7894960

Jones, N P

1994-12-01

359

Orbital blowout fractures in sport.  

PubMed Central

One-third of orbital blowout fractures are sustained during sport. Soccer is most commonly involved. Though visual acuity recovery is usually complete, permanent loss of binocular visual field is almost universal. Typically high-energy blows by opponent's finger, fist, elbow, knee or boot are responsible. Injuries to the eye itself may also be sustained and should be looked for. Ocular protection may be feasible in some sports, but the main preventive measure to be addressed is the reduction in aggressive play or deliberate injury. PMID:7894960

Jones, N P

1994-01-01

360

Assembling the Skylab Orbital Workshop  

NASA Technical Reports Server (NTRS)

This photograph was taken during installation of floor grids on the upper and lower floors inside the Skylab Orbital Workshop at the McDornell Douglas plant at Huntington Beach, California. The OWS was divided into two major compartments. The lower level provided crew accommodations for sleeping, food preparation and consumption, hygiene, waste processing and disposal, and performance of certain experiments. The upper level consisted of a large work area and housed water storage tanks, a food freezer, storage vaults for film, scientific airlocks, mobility and stability experiment equipment, and other experimental equipment.

1970-01-01

361

The Orbiting Carbon Observatory (OCO)  

NASA Technical Reports Server (NTRS)

CO2 is the principal human generated driver of climate change. Accurate forecasting of future climate requires an improved understanding of the global carbon cycle and its interaction with the climate system. The Orbiting Carbon Observatory (OCO) will make global, space-based observations of atmospheric CO2 with the precision, resolution, and coverage needed to understand sources and sinks. OCO data will provide critical information for decision makers including the scientific basis for policy formulation, guide for carbon management strategies and treaty monitoring.

Miller, Charles E.

2005-01-01

362

On-Orbit Software Analysis  

NASA Technical Reports Server (NTRS)

The On-Orbit Software Analysis Research Infusion Project was done by Intrinsyx Technologies Corporation (Intrinsyx) at the National Aeronautics and Space Administration (NASA) Ames Research Center (ARC). The Project was a joint collaborative effort between NASA Codes IC and SL, Kestrel Technology (Kestrel), and Intrinsyx. The primary objectives of the Project were: Discovery and verification of software program properties and dependencies, Detection and isolation of software defects across different versions of software, and Compilation of historical data and technical expertise for future applications

Moran, Susanne I.

2004-01-01

363

An Orbital Maneuvering Vehicle simulator  

NASA Technical Reports Server (NTRS)

The Orbital Maneuvering Vehicle (OMV) is a teleoperated vehicle designed to dock with a target vehicle in space to peform certain tasks. This vehicle is not yet in production, but a simulator of the OMV is located at Marshall Space Flight Center (MSFC). The MSFC facility provides a realistic simulation of the OMV. Various docking maneuvers can be studied in some detail. A special robot has been constructed that provides a moving target for the simulator to dock with. This facility is valuable for conducting studies on the OMV; it also is excellent for personnel training.

Teoh, W.; Walls, J.; Bryan, T.; Roe, F.; Shields, N.

1985-01-01

364

Orbital transfer vehicles - An overview  

NASA Technical Reports Server (NTRS)

A review of past high energy upper stage evolution leading to the first earth-lunar transfer vehicle, the Apollo S-IVB, is given and the current STS (Space Transportation System) upper-stage characteristics are discussed as a basis for future OTV (Orbital Transfer Vehicle) planning. Attention is given to requirements, operational factors, design features, and program alternatives as a background for a general review of OTV planning considerations for STS performance enhancement. The alternative discussed and other issues are under study by NASA and will be carefully assessed during the next few years as options are considered versus mission needs.

Disher, J. H.; Fero, L. K.

1979-01-01

365

Pearls of Orbital Trauma Management  

PubMed Central

Orbital fractures account for a significant portion of traumatic facial injuries. Although plastic surgery literature is helpful, additional pearls and insights are provided in this article from the experience of an oculoplastic surgeon. The fundamentals remain the same, but the perceptions differ and provide a healthy perspective on a long-standing issue. The most important thing to remember is that the optimal management plan is often variable, and the proper choice regarding which plan to choose rests upon the clinical scenario and the surgeon having an honest perception of his or her level of expertise and comfort level. PMID:22550464

Roth, Forrest S.; Koshy, John C.; Goldberg, Jonathan S.; Soparkar, Charles N.S.

2010-01-01

366

Mars Climate Orbiter Mishap Report  

NSDL National Science Digital Library

This Review Panel Report represents the work of a review team contracted by NASA to analyze its programs and practices. Released this week, the report discusses findings relating to the failure of the Mars Climate Orbiter on September 23, 1999. The report also summarizes lessons learned from the mishap, gives an overview of NASA project management, identifies common themes related to recent failures, and makes recommendations for improving the likelihood of future success for NASA missions. An additional report, from the Mars Independent Assessment Team chaired by Thomas Young, will be available by the end of March.

367

Calibration effects on orbit determination  

NASA Technical Reports Server (NTRS)

The effects of charged particle and tropospheric calibrations on the orbit determination (OD) process are analyzed. The calibration process consisted of correcting the Doppler observables for the media effects. Calibrated and uncalibrated Doppler data sets were used to obtain OD results for past missions as well as Mariner Mars 1971. Comparisons of these Doppler reductions show the significance of the calibrations. For the MM'71 mission, the media calibrations proved themselves effective in diminishing the overall B-plane error and reducing the Doppler residual signatures.

Madrid, G. A.; Winn, F. B.; Zielenbach, J. W.; Yip, K. B.

1974-01-01

368

Photometric Orbits of Extrasolar Planets  

NASA Astrophysics Data System (ADS)

We define and analyze the photometric orbit (PhO) of an extrasolar planet observed in reflected light. In our definition, the PhO is a Keplerian entity with six parameters: semimajor axis, eccentricity, mean anomaly at some particular time, argument of periastron, inclination angle, and effective radius, which is the square root of the geometric albedo times the planetary radius. Preliminarily, we assume a Lambertian phase function. We study in detail the case of short-period giant planets (SPGPs) and observational parameters relevant to the Kepler mission: 20 ppm photometry with normal errors, 6.5 hr cadence, and three-year duration. We define a relevant "planetary population of interest" in terms of probability distributions of the PhO parameters. We perform Monte Carlo experiments to estimate the ability to detect planets and to recover PhO parameters from light curves. We calibrate the completeness of a periodogram search technique, and find structure caused by degeneracy. We recover full orbital solutions from synthetic Kepler data sets and estimate the median errors in recovered PhO parameters. We treat in depth a case of a Jupiter body-double. For the stated assumptions, we find that Kepler should obtain orbital solutions for many of the 100-760 SPGP that Jenkins & Doyle estimate Kepler will discover. Because most or all of these discoveries will be followed up by ground-based radial velocity observations, the estimates of inclination angle from the PhO may enable the calculation of true companion masses: Kepler photometry may break the "msin i" degeneracy. PhO observations may be difficult. There is uncertainty about how low the albedos of SPGPs actually are, about their phase functions, and about a possible noise floor due to systematic errors from instrumental and stellar sources. Nevertheless, simple detection of SPGPs in reflected light should be robust in the regime of Kepler photometry, and estimates of all six orbital parameters may be feasible in at least a subset of cases.

Brown, Robert A.

2009-09-01

369

Mission Design for the Lunar Reconnaissance Orbiter  

NASA Technical Reports Server (NTRS)

The Lunar Reconnaissance Orbiter (LRO) will be the first mission under NASA's Vision for Space Exploration. LRO will fly in a low 50 km mean altitude lunar polar orbit. LRO will utilize a direct minimum energy lunar transfer and have a launch window of three days every two weeks. The launch window is defined by lunar orbit beta angle at times of extreme lighting conditions. This paper will define the LRO launch window and the science and engineering constraints that drive it. After lunar orbit insertion, LRO will be placed into a commissioning orbit for up to 60 days. This commissioning orbit will be a low altitude quasi-frozen orbit that minimizes stationkeeping costs during commissioning phase. LRO will use a repeating stationkeeping cycle with a pair of maneuvers every lunar sidereal period. The stationkeeping algorithm will bound LRO altitude, maintain ground station contact during maneuvers, and equally distribute periselene between northern and southern hemispheres. Orbit determination for LRO will be at the 50 m level with updated lunar gravity models. This paper will address the quasi-frozen orbit design, stationkeeping algorithms and low lunar orbit determination.

Beckman, Mark

2007-01-01

370

A method for classifying orbits near asteroids  

NASA Astrophysics Data System (ADS)

A method for classifying orbits near asteroids under a polyhedral gravitational field is presented, and may serve as a valuable reference for spacecraft orbit design for asteroid exploration. The orbital dynamics near asteroids are very complex. According to the variation in orbit characteristics after being affected by gravitational perturbation during the periapsis passage, orbits near an asteroid can be classified into 9 categories: (1) surrounding-to-surrounding, (2) surrounding-to-surface, (3) surrounding-to-infinity, (4) infinity-to-infinity, (5) infinity-to-surface, (6) infinity-to-surrounding, (7) surface-to-surface, (8) surface-to-surrounding, and (9) surface-to-infinity. Assume that the orbital elements are constant near the periapsis, the gravitation potential is expanded into a harmonic series. Then, the influence of the gravitational perturbation on the orbit is studied analytically. The styles of orbits are dependent on the argument of periapsis, the periapsis radius, and the periapsis velocity. Given the argument of periapsis, the orbital energy before and after perturbation can be derived according to the periapsis radius and the periapsis velocity. Simulations have been performed for orbits in the gravitational field of 216 Kleopatra. The numerical results are well consistent with analytic predictions.

Wang, Xian-Yu; Gong, Sheng-Ping; Li, Jun-Feng

2014-06-01

371

A feedback linearization approach to orbital maneuvers  

NASA Astrophysics Data System (ADS)

New methods for obtaining optimal orbital maneuvers of a space vehicle in total velocity change are described and applied. The elegance of Lambert's Theorem is combined with feedback linearization and linear optimal control to obtain solutions to nonlinear orbital maneuver problems. In particular, geocentric orbital maneuvers with finite-thrust acceleration are studied. The full nonlinear equations of motion are transformed exactly into a controllable linear set in Brunovsky canonical form by using feedback linearization and choosing the position vector as the fully observable output vector. These equations are used to pose a linear optimal tracking problem with a solution to the Lambert's impulsive-thrust two-point boundary-value problem as the reference orbit. The same procedure is used to force the space vehicle to follow a linear analytical solution to the continuous low-thrust orbital maneuver problem between neighboring orbits. Limits on thrust magnitudes are enforced by adjusting the weights on the states in the performance index, which is chosen to be the sum of integrals of the square sum of new control variables and the square sum of state variable errors from the reference trajectory. For comparison purpose, the feedback linearized equations are used to obtain a simple closed-form solution to an orbital maneuver problem without the use of a reference trajectory. In this case, the performance index was chosen as the integral of the square sum of new control variables only. Three different examples, coplanar rendezvous between neighboring orbits, large coplanar orbit transfer, and non-coplanar orbit transfer, are used to show the advantages of using the new methods introduced in this dissertation. The minimum-eccentricity orbit, Hohmann transfer orbit, and minimum energy orbit were used in turn as the reference trajectories. The principal problems encountered in using the new methods are the choices of the proper reference trajectory, a suitable time-dependent scalar weighting function, and appropriate constant weighting matrices.

Lee, Sanguk

372

Orbital Pseudotumor: Distinct Diagnostic Features and Management  

PubMed Central

Purpose: To provide an overview of the spectrum of diseases known as ‘idiopathic orbital inflammatory syndrome’ also known as orbital pseudotumor, with emphasis on specific diagnostic challenges in the evaluation and management of patients with this disorder. Methods: Review of the relevant literature and summarize recent findings regarding the epidemiology, diagnosis, pathophysiology and treatment of orbital pseudotumor. Results: Orbital pseudotumor is a benign intraorbital process confined to the orbit but extra orbital involvement can occur. It is among the 3rd most common orbital diseases along with thyroid orbitopathy and lymphoproliferative disorder and accounts for 5-10% of orbital processes. Clinically, orbital pseudotumor has been categorized as myositis, dacryoadenitis, anterior, apical and diffuse process. Patients may present with diplopia, conjunctival chemosis, proptosis or abnormal computed tomography scan (CT-scan) findings. Patients may also have associated optic neuropathy. Diagnosis is based on careful history, ultrasonography (U/S), CT-scan and magnetic resonance imaging (MRI) studies which may also provide prognostic information. Treatment consists of systemic corticosteroids in the form of oral or intravenous administration. Confirmation is made by orbital biopsy. In addition to radiation, cytotoxic agents, immunosuppressant, IV immunoglobulin, biological therapy, TNF-alpha inhibitor monoclonal antibody and Mycophenolate Moftil have been found to be useful in the management of refractory orbital pseudotumor. Conclusion: Understanding of the clinical features of patients with orbital pseudotumor, differentiating it from other orbital processes by use of imaging techniques and timely implementation of available treatment strategies may help prevent visual loss and associated morbidity from this condition. PMID:20379424

Chaudhry, Imtiaz A; Shamsi, Farrukh A; Arat, Yonca O; Riley, Fenwick C

2008-01-01

373

COMET C/2011 W3 (LOVEJOY): ORBIT DETERMINATION, OUTBURSTS, DISINTEGRATION OF NUCLEUS, DUST-TAIL MORPHOLOGY, AND RELATIONSHIP TO NEW CLUSTER OF BRIGHT SUNGRAZERS  

SciTech Connect

We describe the physical and orbital properties of C/2011 W3. After surviving perihelion passage, the comet was observed to undergo major physical changes. The permanent loss of the nuclear condensation and the formation of a narrow spine tail were observed first at Malargue, Argentina, on December 20 and then systematically at Siding Spring, Australia. The process of disintegration culminated with a terminal fragmentation event on December 17.6 UT. The postperihelion dust tail, observed for {approx}3 months, was the product of activity over <2 days. The nucleus' breakup and crumbling were probably caused by thermal stress due to the penetration of the intense heat pulse deep into the nucleus' interior after perihelion. The same mechanism may be responsible for cascading fragmentation of sungrazers at large heliocentric distances. The delayed response to the hostile environment in the solar corona is at odds with the rubble-pile model, since the residual mass of the nucleus, estimated at {approx}10{sup 12} g (equivalent to a sphere 150-200 m across) just before the terminal event, still possessed nontrivial cohesive strength. The high production rates of atomic oxygen, observed shortly after perihelion, are compatible with a subkilometer-sized nucleus. The spine tail-the product of the terminal fragmentation-was a synchronic feature, whose brightest part contained submillimeter-sized dust grains, released at velocities of up to 30 m s{sup -1}. The loss of the nuclear condensation prevented an accurate orbital-period determination by traditional techniques. Since the missing nucleus must have been located on the synchrone, whose orientation and sunward tip have been measured, we compute the astrometric positions of this missing nucleus as the coordinates of the points of intersection of the spine tail's axis with the lines of forced orbital-period variation, derived from the orbital solutions based on high-quality preperihelion astrometry from the ground. The resulting orbit gives 698 {+-} 2 yr for the osculating orbital period, showing that C/2011 W3 is the first member of the expected new, 21st-century cluster of bright Kreutz-system sungrazers, whose existence was predicted by these authors in 2007. From the spine tail's evolution, we determine that its measured tip, populated by dust particles 1-2 mm in diameter, receded antisunward from the computed position of the missing nucleus. The bizarre appearance of the comet's dust tail in images taken only hours after perihelion with the coronagraphs on board the SOHO and STEREO spacecraft is readily understood. The disconnection of the comet's head from the tail released before perihelion and an apparent activity attenuation near perihelion have a common cause-sublimation of all dust at heliocentric distances smaller than about 1.8 solar radii. The tail's brightness is strongly affected by forward scattering of sunlight by dust. From an initially broad range of particle sizes, the grains that were imaged the longest had a radiation-pressure parameter {beta} {approx_equal} 0.6, diagnostic of submicron-sized silicate grains and consistent with the existence of the dust-free zone around the Sun. The role and place of C/2011 W3 in the hierarchy of the Kreutz system and its genealogy via a 14th-century parent suggest that it is indirectly related to the celebrated sungrazer X/1106 C1, which, just as the first-generation parent of C/2011 W3, split from a common predecessor during the previous return to perihelion.

Sekanina, Zdenek; Chodas, Paul W., E-mail: Zdenek.Sekanina@jpl.nasa.gov, E-mail: Paul.W.Chodas@jpl.nasa.gov [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States)

2012-10-01

374

On-orbit Passive Thermography  

NASA Technical Reports Server (NTRS)

On July 12, 2006, British-born astronaut Piers Sellers became the first person to conduct thermal nondestructive evaluation experiments in space, demonstrating the feasibility of a new tool for detecting damage to the reinforced carbon-carbon (RCC) structures of the Shuttle. This new tool was an EVA (Extravehicular Activity, or spacewalk) compatible infrared camera developed by NASA engineers. Data was collected both on the wing leading edge of the Orbiter and on pre-damaged samples mounted in the Shuttle s cargo bay. A total of 10 infrared movies were collected during the EVA totaling over 250 megabytes of data. Images were downloaded from the orbiting Shuttle to Johnson Space Center for analysis and processing. Results are shown to be comparable to ground-based thermal inspections performed in the laboratory with the same type of camera and simulated solar heating. The EVA camera system detected flat-bottom holes as small as 2.54cm in diameter with 50% material loss from the back (hidden) surface in RCC during this first test of the EVA IR Camera. Data for the time history of the specimen temperature and the capability of the inspection system for imaging impact damage are presented.

Howell, Patricia A.; Winfree, William P.; Cramer, K. Elliott

2008-01-01

375

Constrained orbital intercept-evasion  

NASA Astrophysics Data System (ADS)

An effective characterization of intercept-evasion confrontations in various space environments and a derivation of corresponding solutions considering a variety of real-world constraints are daunting theoretical and practical challenges. Current and future space-based platforms have to simultaneously operate as components of satellite formations and/or systems and at the same time, have a capability to evade potential collisions with other maneuver constrained space objects. In this article, we formulate and numerically approximate solutions of a Low Earth Orbit (LEO) intercept-maneuver problem in terms of game-theoretic capture-evasion guaranteed strategies. The space intercept-evasion approach is based on Liapunov methodology that has been successfully implemented in a number of air and ground based multi-player multi-goal game/control applications. The corresponding numerical algorithms are derived using computationally efficient and orbital propagator independent methods that are previously developed for Space Situational Awareness (SSA). This game theoretical but at the same time robust and practical approach is demonstrated on a realistic LEO scenario using existing Two Line Element (TLE) sets and Simplified General Perturbation-4 (SGP-4) propagator.

Zatezalo, Aleksandar; Stipanovic, Dusan M.; Mehra, Raman K.; Pham, Khanh

2014-06-01

376

Orbit control of SPOT satellites  

NASA Astrophysics Data System (ADS)

The SPOT system has been operational since the February 22nd, 1986, SPOT 1 launch date. SPOT 2, the second satellite, was put in orbit on February 21st, 1990, and station acquisition of SPOT 3, the last first generation satellite, was successfully performed after the September 26th, 1993 Ariane launch. Now, three satellites are in orbit, and their relative positions depend on the station keeping requirements specified for each one. Only SPOT 2 and SPOT 3 products are presently commercialized, SPOT 1 being kept in standby. The purpose of this document is to explain the flight dynamics aspects of the system. It synthesizes the specifications related to this field, and recalls specific data resulting from the mission analysis. Described in detail are the station acquisition (referring to the operational results of SPOT 3 launch), launch phase, description of the operations, station acquisition, maneuvers strategy, definition of the parameters monitored for station keeping, automatic management of maneuvers, and relative deviation of the 3 satellites.

Darrigan, Christian; Dulot, Jean-Louis; Forcioli, Dominique; Micheau, Pascal

377

Introducing the Moon's Orbital Eccentricity  

NASA Astrophysics Data System (ADS)

I present a novel way to introduce the lunar orbital eccentricity in introductory astronomy courses. The Moon is perhaps the clearest illustration of the general orbital elements such as inclination, ascending node, eccentricity, perigee, and so on. Furthermore, I like the students to discover astronomical phenomena for themselves, by means of a guided exercise, rather than just telling them the facts.1 The inclination and nodes may be found by direct observation, monitoring carefully the position of the Moon among the stars. Even the regression of the nodes may be discovered in this way2 To find the eccentricity from students' observations is also possible,3 but that requires considerable time and effort. if a whole class should discover it in a short time, here is a method more suitable for a one-day class or home assignment. The level I aim at is, more or less, advanced high school or first-year college students. I assume them to be acquainted with celestial coordinates and the lunar phases, and to be able to use algebra and trigonometry.

Oostra, Benjamin

2014-11-01

378

Superfluid Helium Orbital Resupply Coupling  

NASA Technical Reports Server (NTRS)

The resupply of superfluid helium to satellites and other space-based experiment packages can increase the useful longevity of these devices far beyond their present life expectancies which are many times determined by the supply of helium coolant. The transfer of superfluid helium to spacecraft in space will require a reusable coupling that functions at 1.8 Kelvin with little heat leak and low pressure drop. Moog has designed the Helium Resupply Coupling to meet these operational requirements. Initially, the coupling manual mode operation will be demonstrated on orbit by an EVA crew member during the Space Shuttle borne Superfluid Helium On-Orbit Transfer (SHOOT) experiment. The ultimate application will use robotic (automatic) coupling operation to which the present design readily adapts. The utilization of Moog's exclusive Rotary Shut-Off (RSO) technology in the development of the Superfluid Helium Resupply Coupling is described. The coupling not only performs the function of a flow control valve and disconnect but also provides adequate safety features for a shuttle launched man-rated payload. In addition, the coupling incorporates the necessary features to provide the high thermal isolation of the internal flow path from the external environment.

Ryder, M. O.; Morash, D. H.; Schoenberg, R. J.

1989-01-01

379

Safety in earth orbit study. Volume 4: Space shuttle orbiter: Safety requirements and guidelines on-orbit phase  

NASA Technical Reports Server (NTRS)

Safety requirements and guidelines are listed for the space shuttle orbiter and for its interface with other vehicles. The requirements and guidelines are specific to the hazards and emergencies in earth orbit. The requirements and guidelines for the orbiter are those with respect to vehicle design, safety devices, warning devices, operational procedures, and residual hazards. The requirements and guidelines for interface with the space station, upper stage vehicles, and sortie payloads are imposed on these vehicles to ensure the safety of the shuttle orbiter. The rationale for the safety requirements and guidelines is also discussed.

1972-01-01

380

Application of two special orbits in the orbit determination of lunar satellites  

NASA Astrophysics Data System (ADS)

Using inter-satellite range data, the combined autonomous orbit determination problem of a lunar satellite and a probe on some special orbits is studied in this paper. The problem is firstly studied in the circular restricted three-body problem, and then generalized to the real force model of the Earth-Moon system. Two kinds of special orbits are discussed: collinear libration point orbits and distant retrograde orbits. Studies show that the orbit determination accuracy in both cases can reach that of the observations. Some important properties of the system are carefully studied. These findings should be useful in the future engineering implementation of this conceptual study.

Liu, Peng; Hou, Xi-Yun; Tang, Jing-Shi; Liu, Lin

2014-10-01

381

Orbit Design of Earth-Observation Satellite  

NASA Astrophysics Data System (ADS)

The purpose of this study is to design a reliable orbit for a medium-resolution scientific satellite to observe Earth for developmental issues such as water resources, agricultural, and industrial. To meet this objective this study firstly, defines the mission, secondly, determines mission constraints, thirdly, design the attitude and orbit control system. As for the observation requirements, and the revisit time are provided as a function of the orbital parameters. Initial orbital parameters are obtained by optimal analysis between observation characteristics and attitude and orbit maintenance costs. Long term station-keeping strategies will be provided for the proposed solutions. Impulsive control will be investigated to provide a reliable and affordable attitude and orbit control system.

Owis, Ashraf

382

RHIC BPM system average orbit calculations  

SciTech Connect

RHIC beam position monitor (BPM) system average orbit was originally calculated by averaging positions of 10000 consecutive turns for a single selected bunch. Known perturbations in RHIC particle trajectories, with multiple frequencies around 10 Hz, contribute to observed average orbit fluctuations. In 2006, the number of turns for average orbit calculations was made programmable; this was used to explore averaging over single periods near 10 Hz. Although this has provided an average orbit signal quality improvement, an average over many periods would further improve the accuracy of the measured closed orbit. A new continuous average orbit calculation was developed just prior to the 2009 RHIC run and was made operational in March 2009. This paper discusses the new algorithm and performance with beam.

Michnoff,R.; Cerniglia, P.; Degen, C.; Hulsart, R.; et al.

2009-05-04

383

Mars Observer trajectory and orbit design  

NASA Technical Reports Server (NTRS)

The Mars Observer launch, interplanetary, Mars orbit insertion, and mapping orbit designs are described. The design objective is to enable a near-maximum spacecraft mass to be placed in orbit about Mars. This is accomplished by keeping spacecraft propellant requirements to a minimum, selecting a minimum acceptable launch period, equalizing the spacecraft velocity change requirement at the beginning and end of the launch period, and constraining the orbit insertion maneuvers to be coplanar. The mapping orbit design objective is to provide the opportunity for global observation of the planet by the science instruments while facilitating the spacecraft design. This is realized with a sun-synchronous near-polar orbit whose ground-track pattern covers the planet at progressively finer resolution.

Beerer, Joseph G.; Roncoli, Ralph B.

1991-01-01

384

Acquisition and correction of SPOT 1 orbit  

NASA Astrophysics Data System (ADS)

The orbit selected for the French terrestrial remote-sensing satellite SPOT is characterized, and the procedures used for orbit acquisition and maintenance are explained. The effects of geopotential, lunisolar potential, and atmospheric drag on the orbit are analyzed; the planned rendezvous, inclination, and small phasing corrections are described; and numerical performance data are presented in a chronological account of the first months of SPOT operation.

Serreault, B.

1986-10-01

385

Simulator Study of Lunar Orbit Establishment  

NASA Technical Reports Server (NTRS)

Simulator Study of Lunar Orbit Establishment. The film was made using the Lunar Orbit and Landing Approach Simulator (LOLA). It represents the view an astronaut would see if he were looking toward the lunar horizon just prior to and during retrofire for orbit establishment. During this period the astronaut is essentially flying backward, therefore the lunar surface features appear to be moving away during the flight. [Entire movie available on DVD from CASI as Doc ID 20070030976. Contact help@sti.nasa.gov

1965-01-01

386

The orbits of the satellites of Neptune  

Microsoft Academic Search

This article presents the results of a fit of numerically integrated Neptunian satellite orbits to earth-based astrometric observations and early Voyager spacecraft observations. Ephemerides based on these orbits were used by the Voyager project as the final pre-encounter ephemerides. As a by-product of the orbit fits, estimates of the Neptune mass, the second zonal harmonic of Neptune, and the pole

R. A. Jacobson

1990-01-01

387

Orbit squeezing in a magnetic well  

Microsoft Academic Search

It is shown that the size of a charged particle’s drift orbit is squeezed, i.e., reduced, in a magnetic well in tokamak plasmas. The squeezing factor depends on the energy of the particle, being larger for higher-energy particles. Therefore, for high-energy particles, the size of the drift orbit depends only on the magnetic geometry. These energy-independent drift orbits are also

K. C. Shaing; M. C. Zarnstorff; C. T. Hsu

1996-01-01

388

Orbit squeezing in a magnetic well  

Microsoft Academic Search

It is shown that the size of a charged particle`s drift orbit is squeezed, i.e., reduced, in a magnetic well in tokamak plasmas. The squeezing factor depends on the energy of the particle, being larger for higher-energy particles. Therefore, for high-energy particles, the size of the drift orbit depends only on the magnetic geometry. These energy-independent drift orbits are also

K. C. Shaing; M. C. Zarnstorff; C. T. Hsu

1996-01-01

389

NORAD TLE Conversion from Osculating Orbital Element  

NASA Astrophysics Data System (ADS)

The NORAD type Two Line Element (TLE) was obtained from the osculating orbital elements by an iterative approximation procedure. The mathematical model was presented and computer program was developed for the conversion. The osculating orbital elements of the KOMPSAT-1 were converted into the NORAD TLE. Then the effect of the SGP4 atmospheric drag coefficient (B*) was analyzed by comparison of the orbit propagation results with different B* values.

Lee, Byoung-Sun

2002-12-01

390

Orbiter avionics aim at high reliability  

Microsoft Academic Search

Avionics and astrionics instrumentation, onboard computer system, and data displays of Orbiter are sketched. Information is provided on fly-by-wire guidance, radio altimeters, the Orbiter landing, mission timer (giving cumulative mission time readout and event timing), functions of the Shuttle Avionics Integration Laboratory (SAIL), and the HAL\\/S program language developed for the five Orbiter computers. Crossfeed of data between the five

K. J. Stein

1976-01-01

391

Tidal Decay of Close Planetary Orbits  

Microsoft Academic Search

The 4.2-day orbit of the newly discovered planet around 51~Pegasi is formally\\u000aunstable to tidal dissipation. However, the orbital decay time in this system\\u000ais longer than the main-sequence lifetime of the central star. Given our best\\u000acurrent understanding of tidal interactions, a planet of Jupiter's mass around\\u000aa solar-like star could have dynamically survived in an orbit with a

F. A. Rasio; C. A. Tout; S. H. Lubow; M. Livio

1996-01-01

392

Orbital Debris and NASA's Measurement Program  

NASA Astrophysics Data System (ADS)

Since the launch of Sputnik in 1957, the number of manmade objects in orbit around the Earth has dramatically increased. The United States Space Surveillance Network (SSN) tracks and maintains orbits on over nine thousand objects down to a limiting diameter of about ten centimeters. Unfortunately, active spacecraft are only a small percentage ( ~ 7%) of this population. The rest of the population is orbital debris or ``space junk" consisting of expended rocket bodies, dead payloads, bits and pieces from satellite launches, and fragments from satellite breakups. The number of these smaller orbital debris objects increases rapidly with decreasing size. It is estimated that there are at least 130,000 orbital debris objects between one and ten centimeters in diameter. Most objects smaller than 10 centimeters go untracked! As the orbital debris population grows, the risk to other orbiting objects, most importantly manned space vehicles, of a collision with a piece of debris also grows. The kinetic energy of a solid 1 cm aluminum sphere traveling at an orbital velocity of 10 km/sec is equivalent to a 400 lb. safe traveling at 60 mph. Fortunately, the volume of space in which the orbiting population resides is large, collisions are infrequent, but they do occur. The Space Shuttle often returns to earth with its windshield pocked with small pits or craters caused by collisions with very small, sub-millimeter-size pieces of debris (paint flakes, particles from solid rocket exhaust, etc.), and micrometeoroids. To get a more complete picture of the orbital-debris environment, NASA has been using both radar and optical techniques to monitor the orbital debris environment. This paper gives an overview of the orbital debris environment and NASA's measurement program.

Africano, J. L.; Stansbery, E. G.

2002-05-01

393

Orbital subcycles for Earth remote sensing satellites  

Microsoft Academic Search

In this paper 1 review the reasons why it is desirable to place a remote-sensing satellite into an orbit which periodically repeats its path. Such exactly-repeating orbits are often used for Earth remote-sensing satellites, but the most appropriate orbit depends upon the likely application of the data. If they are to be used to study a rapidly changing phenomenon a

W. G. REES

1992-01-01

394

Large capacity cryopropellant orbital storage facility  

NASA Technical Reports Server (NTRS)

A comprehensive study was performed to develop the major features of a large capacity orbital propellant storage facility for the space-based cryogenic orbital transfer vehicle. Projected propellant usage and delivery schedules can be accommodated by two orbital tank sets of 100,000 lb storage capacity, with advanced missions expected to require increased capacity. Information is given on tank pressurization schemes, propellant transfer configurations, pump specifications, the refrigeration system, and flight tests.

Schuster, J. R.

1987-01-01

395

Angle resolved photoemission from organic semiconductors: orbital imaging beyond the molecular orbital interpretation  

NASA Astrophysics Data System (ADS)

Fascinating pictures that can be interpreted as showing molecular orbitals have been obtained with various imaging techniques. Among these, angle resolved photoemission spectroscopy (ARPES) has emerged as a particularly powerful method. Orbital images have been used to underline the physical credibility of the molecular orbital concept. However, from the theory of the photoemission process it is evident that imaging experiments do not show molecular orbitals, but Dyson orbitals. The latter are not eigenstates of a single-particle Hamiltonian and thus do not fit into the usual simple interpretation of electronic structure in terms of molecular orbitals. In a combined theoretical and experimental study we thus check whether a Dyson-orbital and a molecular-orbital based interpretation of ARPES lead to differences that are relevant on the experimentally observable scale. We discuss a scheme that allows for approximately calculating Dyson orbitals with moderate computational effort. Electronic relaxation is taken into account explicitly. The comparison reveals that while molecular orbitals are frequently good approximations to Dyson orbitals, a detailed understanding of photoemission intensities may require one to go beyond the molecular orbital picture. In particular we clearly observe signatures of the Dyson-orbital character for an adsorbed semiconductor molecule in ARPES spectra when these are recorded over a larger momentum range than in earlier experiments.

Dauth, M.; Wiessner, M.; Feyer, V.; Schöll, A.; Puschnig, P.; Reinert, F.; Kümmel, S.

2014-10-01

396

TOPEX/Poseidon orbit acquisition maneuver design  

NASA Astrophysics Data System (ADS)

The current baseline injection orbit for the jointly sponsored NASA/CNES TOPEX/Poseidon mission is near-circular, approximately 30 km below the desired operational orbit altitude and at the operational orbit inclination. A baseline maneuver sequence to retarget from this injection orbit to the desired operational orbit has been designed based upon the expected worst-case 3-sigma injection and maneuver execution errors. The sequence requires seven maneuvers, including an initial calibration burn, and achieves the operational orbit with the desired ground track pattern in 30 days. A delay sensitivity analysis has been conducted to estimate the allowable operational delay for each maneuver without increasing the total orbit acquisition period. The baseline sequence provides back-ups for a one-revolution delay for each maneuver and one-day delay for most maneuvers. It is also shown that a higher injection orbit allows the maneuver sequence to achieve the operational orbit in 26 days under a worst-case scenario.

Bhat, Ramachandra S.

1992-08-01

397

TOPEX/Poseidon orbit acquisition maneuver design  

NASA Technical Reports Server (NTRS)

The current baseline injection orbit for the jointly sponsored NASA/CNES TOPEX/Poseidon mission is near-circular, approximately 30 km below the desired operational orbit altitude and at the operational orbit inclination. A baseline maneuver sequence to retarget from this injection orbit to the desired operational orbit has been designed based upon the expected worst-case 3-sigma injection and maneuver execution errors. The sequence requires seven maneuvers, including an initial calibration burn, and achieves the operational orbit with the desired ground track pattern in 30 days. A delay sensitivity analysis has been conducted to estimate the allowable operational delay for each maneuver without increasing the total orbit acquisition period. The baseline sequence provides back-ups for a one-revolution delay for each maneuver and one-day delay for most maneuvers. It is also shown that a higher injection orbit allows the maneuver sequence to achieve the operational orbit in 26 days under a worst-case scenario.

Bhat, Ramachandra S.

1992-01-01

398

Payload/orbiter contamination control assessment support  

NASA Technical Reports Server (NTRS)

The development and use is described of a basic contamination mathematical model of the shuttle orbiter which incorporates specific shuttle orbiter configurations and contamination sources. These configurations and sources were evaluated with respect to known shuttle orbiter operational surface characteristics and specific lines-of-sight which encompass the majority of viewing requirements for shuttle payloads. The results of these evaluations are presented as summary tables for each major source. In addition, contamination minimization studies were conducted and recommendations are made, where applicable, to support the shuttle orbiter design and operational planning for those sources which were identified to present a significant contamination threat.

Rantanen, R. O.; Ress, E. B.

1975-01-01

399

A periodic table for black hole orbits  

SciTech Connect

Understanding the dynamics around rotating black holes is imperative to the success of future gravitational wave observatories. Although integrable in principle, test-particle orbits in the Kerr spacetime can also be elaborate, and while they have been studied extensively, classifying their general properties has been a challenge. This is the first in a series of papers that adopts a dynamical systems approach to the study of Kerr orbits, beginning with equatorial orbits. We define a taxonomy of orbits that hinges on a correspondence between periodic orbits and rational numbers. The taxonomy defines the entire dynamics, including aperiodic motion, since every orbit is in or near the periodic set. A remarkable implication of this periodic orbit taxonomy is that the simple precessing ellipse familiar from planetary orbits is not allowed in the strong-field regime. Instead, eccentric orbits trace out precessions of multileaf clovers in the final stages of inspiral. Furthermore, for any black hole, there is some point in the strong-field regime past which zoom-whirl behavior becomes unavoidable. Finally, we sketch the potential application of the taxonomy to problems of astrophysical interest, in particular its utility for computationally intensive gravitational wave calculations.

Levin, Janna [Department of Physics and Astronomy, Barnard College of Columbia University, 3009 Broadway, New York, New York 10027 (United States); Institute for Strings, Cosmology and Astroparticle Physics, Columbia University, New York, New York 10027 (United States); Perez-Giz, Gabe [Physics Department, Columbia University, New York, New York 10027 (United States)

2008-05-15

400

On-Orbit Compressor Technology Program  

NASA Technical Reports Server (NTRS)

A synopsis of the On-Orbit Compressor Technology Program is presented. The objective is the exploration of compressor technology applicable for use by the Space Station Fluid Management System, Space Station Propulsion System, and related on-orbit fluid transfer systems. The approach is to extend the current state-of-the-art in natural gas compressor technology to the unique requirements of high-pressure, low-flow, small, light, and low-power devices for on-orbit applications. This technology is adapted to seven on-orbit conceptual designs and one prototype is developed and tested.

Deffenbaugh, Danny M.; Svedeman, Steven J.; Schroeder, Edgar C.; Gerlach, C. Richard

1990-01-01

401

Space Shuttle orbiter approach and landing test  

NASA Technical Reports Server (NTRS)

The Approach and Landing Test Program consisted of a series of steps leading to the demonstration of the capability of the Space Shuttle orbiter to safely approach and land under conditions similar to those planned for the final phases of an orbital flight. The tests were conducted with the orbiter mounted on top of a specially modified carrier aircraft. The first step provided airworthiness and performance verification of the carrier aircraft after modification. The second step consisted of three taxi tests and five flight tests with an inert unmanned orbiter. The third step consisted of three mated tests with an active manned orbiter. The fourth step consisted of five flights in which the orbiter was separated from the carrier aircraft. For the final two flights, the orbiter tail cone was replaced by dummy engines to simulate the actual orbital configuration. Landing gear braking and steering tests were accomplished during rollouts following the free flight landings. Ferry testing was integrated into the Approach and Landing Test Program to the extent possible. In addition, four ferry test flights were conducted with the orbiter mated to the carrier aircraft in the ferry configuration after the free-flight tests were completed.

1978-01-01

402

Determination of GPS orbits to submeter accuracy  

NASA Technical Reports Server (NTRS)

Orbits for satellites of the Global Positioning System (GPS) were determined with submeter accuracy. Tests used to assess orbital accuracy include orbit comparisons from independent data sets, orbit prediction, ground baseline determination, and formal errors. One satellite tracked 8 hours each day shows rms error below 1 m even when predicted more than 3 days outside of a 1-week data arc. Differential tracking of the GPS satellites in high Earth orbit provides a powerful relative positioning capability, even when a relatively small continental U.S. fiducial tracking network is used with less than one-third of the full GPS constellation. To demonstrate this capability, baselines of up to 2000 km in North America were also determined with the GPS orbits. The 2000 km baselines show rms daily repeatability of 0.3 to 2 parts in 10 to the 8th power and agree with very long base interferometry (VLBI) solutions at the level of 1.5 parts in 10 to the 8th power. This GPS demonstration provides an opportunity to test different techniques for high-accuracy orbit determination for high Earth orbiters. The best GPS orbit strategies included data arcs of at least 1 week, process noise models for tropospheric fluctuations, estimation of GPS solar pressure coefficients, and combine processing of GPS carrier phase and pseudorange data. For data arc of 2 weeks, constrained process noise models for GPS dynamic parameters significantly improved the situation.

Bertiger, W. I.; Lichten, S. M.; Katsigris, E. C.

1988-01-01

403

Mars Observer Lecture: Mars Orbit Insertion  

NASA Technical Reports Server (NTRS)

The Mars Observer mission spacecraft was primarily designed for exploring Mars and the Martian environment. The Mars Observer was launched on September 25, 1992. The spacecraft was lost in the vicinity of Mars on August 21, 1993 when the spacecraft began its maneuvering sequence for Martian orbital insertion. This videotape shows a lecture by Suzanne R. Dodd, the Mission Planning Team Chief for the Mars Observer Project. Ms Dodd begins with a brief overview of the mission and the timeline from the launch to orbital insertion. Ms Dodd then reviews slides showing the trajectory of the spacecraft on its trip to Mars. Slides of the spacecraft being constructed are also shown. She then discusses the Mars orbit insertion and the events that will occur to move the spacecraft from the capture orbit into a mapping orbit. During the trip to Mars, scientists at JPL had devised a new strategy, called Power In that would allow for an earlier insertion into the mapping orbit. The talk summarizes this strategy, showing on a slide the planned transition orbits. There are shots of the Martian moon, Phobos, taken from the Viking spacecraft, as Ms Dodd explains that the trajectory will allow the orbiter to make new observations of that moon. She also explains the required steps to prepare for mapping after the spacecraft has achieved the mapping orbit around Mars. The lecture ends with a picture of Mars from the Observer on its approach to the planet.

Dodd, Suzanne R. (Personal Name)

1993-01-01

404

Improved orbiter waste collection system study  

NASA Technical Reports Server (NTRS)

Design concepts for improved fecal waste collection both on the space shuttle orbiter and as a precursor for the space station are discussed. Inflight usage problems associated with the existing orbiter waste collection subsystem are considered. A basis was sought for the selection of an optimum waste collection system concept which may ultimately result in the development of an orbiter flight test article for concept verification and subsequent production of new flight hardware. Two concepts were selected for orbiter and are shown in detail. Additionally, one concept selected for application to the space station is presented.

Bastin, P. H.

1984-01-01

405

A Periodic Table for Black Hole Orbits  

E-print Network

Understanding the dynamics around rotating black holes is imperative to the success of the future gravitational wave observatories. Although integrable in principle, test particle orbits in the Kerr spacetime can also be elaborate, and while they have been studied extensively, classifying their general properties has been a challenge. This is the first in a series of papers that adopts a dynamical systems approach to the study of Kerr orbits, beginning with equatorial orbits. We define a taxonomy of orbits that hinges on a correspondence between periodic orbits and rational numbers. The taxonomy defines the entire dynamics, including aperiodic motion, since every orbit is in or near the periodic set. A remarkable implication of this periodic orbit taxonomy is that the simple precessing ellipse familiar from planetary orbits is not allowed in the strong-field regime. Instead, eccentric orbits trace out precessions of multi-leaf clovers in the final stages of inspiral. Furthermore, for any black hole, there is some point in the strong-field regime past which zoom-whirl behavior becomes unavoidable. Finally, we sketch the potential application of the taxonomy to problems of astrophysical interest, in particular its utility for computationally intensive gravitational wave calculations.

Janna Levin; Gabe Perez-Giz

2008-02-04

406

The accuracy of Halley's cometary orbits  

NASA Astrophysics Data System (ADS)

The accuracy of a scientific computation depends in the main on the data fed in and the analysis method used. This statement is certainly true of Edmond Halley's cometary orbit work. Considering the 420 comets that had been seen before Halley's era of orbital calculation (1695 - 1702) only 24, according to him, had been observed well enough for their orbits to be calculated. Two questions are considered in this paper. Do all the orbits listed by Halley have the same accuracy? and, secondly, how accurate was Halley's method of calculation?

Hughes, D. W.

407

Orbital Operations for Phobos and Deimos Exploration  

NASA Technical Reports Server (NTRS)

One of the deep-space human exploration activities proposed for the post-Shuttle era is a mission to one of the moons of Mars, Phobos or Deimos. There are several options available to the mission architect for operations around these bodies. These options include distant retrograde orbits (DROs), Lagrange-point orbits such as halos and Lyapunov orbits, and fixed-point stationkeeping or "hovering." These three orbit options are discussed in the context of the idealized circular restricted three body problem, full-dynamics propagations, and a concept of operations. The discussion is focused on Phobos, but all results hold for Deimos

Wallace, Mark S.; Parker, Jeffrey S.; Strange, Nathan J.; Grebow, Daniel

2012-01-01

408

New concepts for Mercury orbiter missions  

NASA Technical Reports Server (NTRS)

The next logical step in the exploration of Mercury is an orbiter mission. A conflict exists between those in the field of planetary sciences who desire a mission with a low circular orbit, and scientists in the fields and particles disciplines, who generally prefer a highly elliptical spacecraft orbit. The thermal environment imposed by the sun and planet render the low orbit intolerable for spacecraft using previous thermal control methods. A thermal control concept and a spacecraft mission concept have been developed which resolve these problems and promise a scientifically significant mission for the mid-1980s.

French, J. R.; Stuart, J. R.; Zeldin, B.

1978-01-01

409

Orbit stability of the ALS storage ring  

SciTech Connect

The Advanced Light Source (ALS) storage ring, a synchrotron light source of the third generation, is specified to maintain its electron orbit stable within one tenth of the rms beam size. In the absence of a dedicated orbit feed-back system, several orbit-distorting effects were investigated, aided by a new interactive simulation tool, the code TRACY V. The effort has led to a better understanding of the behavior of a variety of accelerator subsystems and in consequence produced a substantial improvement in day-to-day orbit stability.

Keller, R.; Nishimura, H.; Biocca, A. [and others

1997-05-01

410

Superexchange Interaction in Orbitally Fluctuating RVO3  

NASA Astrophysics Data System (ADS)

Changes in pressure and magnetic field in the orbital and magnetic ordering temperatures of RVO3 perovskites are reported; they reveal a competition between two magnetic orbitally ordered phases that have opposite preferences for the e-orbital component in the localized T1g3 ground state of the V3+ ion. This competition is shown to be biased by the VO6/2 site distortion intrinsic to the orthorhombic structure. A remarkable enhancement of TN with pressure is found where the competition leads to enhanced orbital critical fluctuations.

Zhou, J.-S.; Goodenough, J. B.; Yan, J.-Q.; Ren, Y.

2007-10-01

411

NASA Orbiter Extended Nose Landing Gear  

NASA Technical Reports Server (NTRS)

This paper discusses the design, development, test, and evaluation of a prototype Extended Nose Landing Gear (ENLG) for NASA's Space Shuttle orbiters. The ENLG is a proposed orbiter modification developed in-house at NASA's Johnson Space Center (JSC) by a joint government/industry team. It increases the orbiter's nose landing gear (NLG) length, thereby changing the vehicle's angle of attack during rollout, which lowers the aerodynamic forces on the vehicle. This, in combination with a dynamic elevon change, will lower the loads on the orbiter's main landing gear (MLG). The extension is accomplished by adding a telescoping section to the current NLG strut that will be pneumatically extended during NLG deployment.

King, Steven R.; Jensen, Scott A.; Hansen, Christopher P.

1999-01-01

412

On-orbit coldwelding: Fact or friction?  

NASA Technical Reports Server (NTRS)

A study into the potential of on-orbit coldwelding occurring was completed. No instances of cold welding were found during deintegration and subsequent testing and analysis of LDEF hardware. This finding generated wide interest and indicated the need to review previous on-orbit coldwelding experiments and on-orbit spacecraft anomalies to determine whether the absence of coldwelding on LDEF was to be expected. Results show that even though there have been no documented cases of significant on-orbit coldwelding events occurring, precautions should be taken to ensure that neither coldwelding nor galling occurs in the space or prelaunch environment.

Dursch, Harry; Spear, Steve

1992-01-01

413

LISA Optics and Orbital Motions  

NASA Technical Reports Server (NTRS)

The Laser Interferometer Space Antenna (LISA) telescopes must be able to send to and receive light from the other two distant spacecraft. The angle between the distant spacecraft will vary by about one degree in the course of a year. In addition the send and receive directions, for any one telescope, will also vary because of changes in distance, relative velocities of the spacecraft and the flight time of the light. All of these (angular) motions place requirements on the telescope pointing mechanism and the compensating proof mass motions. In this paper we will present the magnitudes of these angular motions, within the context of Keplerian orbits, and the resulting image motions on the detectors.

Waluschka, Eugene; Scherr, Lawrence M.

2003-01-01

414

Airbreathing Acceleration Toward Earth Orbit  

SciTech Connect

As flight speed increases, aerodynamic drag rises more sharply than the availability of atmospheric oxygen. The ratio of oxygen mass flux to dynamic pressure cannot be improved by changing altitude. The maximum possible speed for airbreathing propulsion is limited by the ratio of air capture area to vehicle drag area, approximately Mach 6 at equal areas. Simulation of vehicle acceleration shows that the use of atmospheric oxygen offers a significant potential for minimizing onboard consumables at low speeds. These fundamental calculations indicate that a practical airbreathing launch vehicle would accelerate to near steady-state speed while consuming only onboard fuel, then transition to rocket propulsion. It is suggested that an aircraft carrying a rocket-propelled vehicle to approximately Mach 5 could be a realistic technical goal toward improving access to orbit.

Whitehead, J C

2007-05-09

415

A remotely controlled orbiting retriever  

NASA Technical Reports Server (NTRS)

A preliminary design effort was recently carried out to investigate methods of removing a certain class of space objects from Shuttle type orbits. Specifically, expired satellites, upper stages, and other objects of potential danger to the Shuttle are the targets of the study. The Trash Remover and Satellite Hauler (TRASH-1) design effort was broken into several disciplines: mission analysis, systems engineering, dynamics and control, power, thermal, and propulsion. A basic requirements is that TRASH-1 go up in the Shuttle. It must be reusable and capable of disposing of more than one item per mission for cost effectiveness. These requirements imply TRASH-1 should use current technology, be modular in design, and be relatively maneuverable. In order to maximize utility, it should be able to both capture and deorbit objects. The design was a basic bus with attachable modules which can either capture or deorbit, depending on the module.

Kaplan, M. H.

1985-01-01

416

A Mercury orbiter mission design  

NASA Technical Reports Server (NTRS)

The paper presents the results of the first stage of a Mercury Orbiter Mission Concept Definition study originated by NASA, with emphasis on a proposed end-to-end mission scenario. The science rationale and the strawman payload are presented, along with the spacecraft design based on a novel use of conventional technology that eliminates the need for high-cost high-risk technology development. A mission scenario demonstrating the capability of conducting desired science investigations is addressed. It is shown that complete imaging coverage of the planet at 1-km or better resolution, and with at least three different phase angles, is possible. Focus is placed on launch period analysis, mission performance, and mission opportunities.

Yen, Chen-Wan L.; Collins, David H.; Meyer, Scott A.

1989-01-01

417

Fibrous dysplasia of the orbit.  

PubMed Central

Twelve patients with fibrous dysplasia of the orbit are reviewed and the ophthalmic findings described. Three case histories are presented in detail. Six patients were managed conservatively; four have shown radiological progression of the disease. Six patients underwent surgery. A conservative procedure, comprising debulking dysplastic bone, was carried out in four--all required further surgery including radical excision in two patients. Two subjects had primary radical operations. No recurrence was encountered in the four patients who had undergone radical surgery. It would appear that fibrous dysplasia is not a disease confined to adolescence but may continue into adulthood, and even middle age. Patients may never require surgery, but require follow up for late progression. If surgical intervention is deemed necessary, an attempt should be made to excise all dysplastic bone, since progression of the disease after conservative surgery is relatively common. Images PMID:8199111

Bibby, K; McFadzean, R

1994-01-01

418

Mars Reconnaissance Orbiter Wrapper Script  

NASA Technical Reports Server (NTRS)

The MRO OLVM wrapper script software allows Mars Reconnaissance Orbiter (MRO) sequence and spacecraft engineers to rapidly simulate a spacecraft command product through a tool that simulates the onboard sequence management software (OLVM). This script parses sequence files to determine the appropriate time boundaries for the sequence, and constructs the script file to be executed by OLVM to span the entirety of the designated sequence. It then constructs script files to be executed by OLVM, constructs the appropriate file directories, populates these directories with needed input files, initiates OLVM to simulate the actual command product that will be sent to the spacecraft, and captures the results of the simulation run to an external file for later review. Additionally, the tool allows a user to manually construct the script, if desired, and then execute the script with a simple command line.

Gladden, Roy; Fisher, Forest; Khanampornpan, Teerapat

2008-01-01

419

Electron vortex orbits and merger  

SciTech Connect

Pure electron plasma columns are contained inside hollow conducting cylinders in an axial magnetic field. In the 2D {ital E}{bold {times}}{ital B} drift approximation, an electron column is a vortex evolving in ({ital r},{theta}) according to the Euler equation. First the center-of-mass orbits of two vortices sufficiently well-separated to be stable to merger are characterized. Equilibria are observed in which the vortices orbit about the center of the cylinder, with either oscillations about stable equilibria or exponential divergence away from unstable equilibria. The equilibrium positions, oscillation frequencies, and instability rates for these spatially extended vortices agree well with the predictions of point vortex theory, apparently because surface waves and shape distortions do not couple significantly to the center-of-mass motion. Next, the merger of two vortices with unequal radii is quantified. Merger is accompanied by the formation of filamentary arms, and results ultimately in an axisymmetric central core surrounded by a lower density halo. The self-energy of the merged core is found to be roughly the sum of the self-energy of the merging vortices. The fraction of the total circulation entrained into the core varies from 70{percent} to 90{percent} as the ratio of the initial vortex radii is varied from 1:1 to 2:1. The point-like vortex dynamics and the circulation loss with merger are both consistent with the {open_quote}{open_quote}punctuated Hamiltonian{close_quote}{close_quote} models of decaying turbulence. {copyright} {ital 1996 American Institute of Physics.}

Mitchell, T.B. [Los Alamos National Laboratory, Los Alamos, New Mexico 87544 (United States)] [Los Alamos National Laboratory, Los Alamos, New Mexico 87544 (United States); Driscoll, C.F. [Department of Physics 0319, University of California at San Diego, La Jolla, California 92093-0319 (United States)] [Department of Physics 0319, University of California at San Diego, La Jolla, California 92093-0319 (United States)

1996-07-01

420

Osteoradionecrosis of the exenterated orbit.  

PubMed

Osteoradionecrosis (ORN) occurs in an estimated 2% of head and neck-irradiated patients. It is seen most commonly in the mandible with other reported sites including the maxilla, temporal bone, clavicle, and vertebrae. It is defined as an area of exposed devitalised irradiated bone, with failure to heal during a period of at least 3 months, in the absence of local neoplastic disease. We report 2 cases of ORN following postoperative radiotherapy given to patients who had undergone an orbital exenteration. ORN can develop spontaneously in one-third of cases, although in the majority of patients, it is induced by secondary trauma. Radiotherapy induces an endarteritis in the small blood vessels of bone, thus favouring the generation of small thrombi that obliterate the vascular lumen and interrupt tissue perfusion. Likewise, irradiation impairs the function of osteoblasts, manifesting as osteopenia, with impairment of the repair and remodelling capacity of bone. Prior radiation exposure can thus decrease bone vascularity and injure its reserve reparative capacity. It is important to differentiate ORN from local recurrence of malignancy, bone metastasis, radiation-induced sarcoma, and infection. CT and MRI are effective diagnostic tools. Clinical management of ORN is complex and unsatisfactory. Treatment remains difficult, and prevention is paramount. A history of radiotherapy should alert clinicians to detect bone exposure or excessively prolonged socket healing. Early diagnosis with a high index of suspicion can achieve higher control rates with conservative management. Our case series reports a rare, previously unreported, but important complication of radiation therapy of the exenterated orbit. PMID:24660959

Peter, Neena M; Laitt, Roger; Leatherbarrow, Brian

2014-06-01

421

Mars Observer Orbit Insertion Briefing  

NASA Technical Reports Server (NTRS)

Steve Wall is the host of this video entitled, "Return to the Red Planet". Live animation of the Mars Observer orbiting Mars is presented. Steve Wall explains the spacecraft insertion maneuver and also explains the purpose for the Mars Observer launch. Live coverage of the Cape Canaveral launch of the Mars Observer is also presented. Suzanne Dodd, Chief of the Mission Planning team describes the burn start and how the spacecraft will be captured by Mars' gravity. Glenn Cunningham, Mars Observer Project Manager, gives background information on the Mars Observer and describes the organizations behind the Mars Observer Spacecraft, such as the Deep Space Network, the Mission Operation Support Office, Science Investigators, the Flight Engineering Office, Operations Office, and the Ground Data System Office. Dr. William Piotrowski, Acting Director, Solar System Exploration Division, NASA, talks about the purpose of the Mars Pathfinder which is to develop the technology and systems for landing small science packages on Mars. Mr. Roger Gibbs, Former Mars Observer Spacecraft Systems Engineer, tells us how the Mars Observer was built and describes the structural elements on the Mars Observer. The 11-month cruise period for the spacecraft is given by Joseph Beerer, Manager of the Engineering office. The thrust for the Mars Orbit Insertion is described by Ronald Klemetson, Technical Manager, Propulsion Subsystem Jet Propulsion Laboratory (JPL). George Chen, Lead Engineer Attitude and Articulation Subsystem Spacecraft Team, explains the importance of the attitude control engines on the Spacecraft. Marvin Traxler, Manager of Tracking and Data Acquisition, describes how searching for a signal from the Mars Observer works. See NONP-NASA-VT-2000081555 for a continuation of this discussion with Marvin Traxler.

1993-01-01

422

Spin-orbit resonances and rotation of coorbital bodies in quasi-circular orbits  

E-print Network

The rotation of asymmetric bodies in eccentric Keplerian orbits can be chaotic when there is some overlap of spin-orbit resonances. Here we show that the rotation of two coorbital bodies (two planets orbiting a star or two satellites of a planet) can also be chaotic even for quasi-circular orbits around the central body. When dissipation is present, the rotation period of a body on a nearly circular orbit is believed to always end synchronous with the orbital period. Here we demonstrate that for coorbital bodies in quasi-circular orbits, stable non-synchronous rotation is possible for a wide range of mass ratios and body shapes. We further show that the rotation becomes chaotic when the natural rotational libration frequency, due to the axial asymmetry, is of the same order of magnitude as the orbital libration frequency.

Robutel, Philippe; Leleu, Adrien

2014-01-01

423

Orbit determination singularities in the Doppler tracking of a planetary orbiter  

NASA Technical Reports Server (NTRS)

On a number of occasions, spacecraft launched by the U.S. have been placed into orbit about the moon, Venus, or Mars. It is pointed out that, in particular, in planetary orbiter missions two-way coherent Doppler data have provided the principal data type for orbit determination applications. The present investigation is concerned with the problem of orbit determination on the basis of Doppler tracking data in the case of a spacecraft in orbit about a natural body other than the earth or the sun. Attention is given to Doppler shift associated with a planetary orbiter, orbit determination using a zeroth-order model for the Doppler shift, and orbit determination using a first-order model for the Doppler shift.

Wood, L. J.

1985-01-01

424

Optimal selection of Orbital Replacement Unit on-orbit spares - A Space Station system availability model  

NASA Technical Reports Server (NTRS)

A mathematical programing model is presented to optimize the selection of Orbital Replacement Unit on-orbit spares for the Space Station. The model maximizes system availability under the constraints of logistics resupply-cargo weight and volume allocations.

Schwaab, Douglas G.

1991-01-01

425

Free space laser communication experiments from Earth to the Lunar Reconnaissance Orbiter in lunar orbit  

E-print Network

Laser communication and ranging experiments were successfully conducted from the satellite laser ranging (SLR) station at NASA Goddard Space Flight Center (GSFC) to the Lunar Reconnaissance Orbiter (LRO) in lunar orbit. ...

Sun, Xiaoli

426

GOCE Satellite Orbit in a Computational Aspect  

NASA Astrophysics Data System (ADS)

The presented work plays an important role in research of possibility of the Gravity Field and Steady-State Ocean Circulation Explorer Mission (GOCE) satellite orbit improvement using a combination of satellite to satellite tracking high-low (SST- hl) observations and gravity gradient tensor (GGT) measurements. The orbit improvement process will be started from a computed orbit, which should be close to a reference ("true") orbit as much as possible. To realize this objective, various variants of GOCE orbit were generated by means of the Torun Orbit Processor (TOP) software package. The TOP software is based on the Cowell 8th order numerical integration method. This package computes a satellite orbit in the field of gravitational and non-gravitational forces (including the relativistic and empirical accelerations). The three sets of 1-day orbital arcs were computed using selected geopotential models and additional accelerations generated by the Moon, the Sun, the planets, the Earth and ocean tides, the relativity effects. Selected gravity field models include, among other things, the recent models from the GOCE mission and the models such as EIGEN-6S, EIGEN-5S, EIGEN-51C, ITG-GRACE2010S, EGM2008, EGM96. Each set of 1-day orbital arcs corresponds to the GOCE orbit for arbitrary chosen date. The obtained orbits were compared to the GOCE reference orbits (Precise Science Orbits of the GOCE satellite delivered by the European Space Agency) using the root mean squares (RMS) of the differences between the satellite positions in the computed orbits and in the reference ones. These RMS values are a measure of performance of selected geopotential models in terms of GOCE orbit computation. The RMS values are given for the truncated and whole geopotential models. For the three variants with the best fit to the reference orbits, the empirical acceleration models were added to the satellite motion model. It allowed for further improving the fitting of computed orbits to the reference orbits. A linear and non-linear model of empirical accelerations was used. After using the non-linear model, the RMS values were reduced by the factor from about 2 to 3 compared with the linear model. A general form of the non-linear model of empirical accelerations is shown in this work. This model can be scaled to a given set of dynamical data for orbit determination by estimating of 192 parameters. The comparison between the computed orbits and the reference ones was performed with respect to the inertial reference frame (IRF) at J2000.0 epoch. Thus, the given GOCE reference orbits were transformed from ITRF2005 reference frame into IRF frame. It is shown that the velocity components of GOCE reference orbits must be transformed into IRF frame using the full rotation vector of the Earth. In such a case RMS values reach a level of meters.

Bobojc, Andrzej; Drozyner, Andrzej

2013-04-01

427

Orbital Dynamics of Low-Earth Orbit Laser-Propelled Space Vehicles  

SciTech Connect

Trajectories applicable to laser-propelled space vehicles with a laser station in low-Earth orbit are investigated. Laser vehicles are initially located in the vicinity of the Earth-orbiting laser station in low-earth orbit at an altitude of several hundreds kilometers, and are accelerated by laser beaming from the laser station. The laser-propelled vehicles start from low-earth orbit and finally escape from the Earth gravity well, enabling interplanetary trajectories and planetary exploration.

Yamakawa, Hiroshi [Research Institute for Sustainable Humanosphere, Kyoto University, Gokasho, Uji, Kyoto, 611-0011 (Japan); Funaki, Ikkoh [Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1, Yoshinodai, Sagamihara, Kanagawa, 229-8510 (Japan); Komurasaki, Kimiya [Department of Advanced Energy, University of Tokyo, 5-1-5, Kashiwanoha, Kashiwa, Chiba, 277-8561 (Japan)

2008-04-28

428

Trimer effects in fragment molecular orbital-linear combination of molecular orbitals calculation of one-electron orbitals for biomolecules.  

PubMed

The fragment molecular orbital (FMO)-linear combination of molecular orbitals (LCMO) method incorporates as an efficient post-process calculation of one-electron orbitals of the whole system after the FMO total energy calculation. A straightforward way to increase the accuracy is inclusion of the trimer effect. Here, we derive a comprehensive formulation called the FMO3-LCMO method. To keep the computational costs of the trimer term low enough, we use a matrix-size reduction technique. We evaluated the accuracy and efficiency of the FMO3-LCMO scheme in model biological systems (alanine oligomer and chignolin). The results show that delocalized electronic orbitals with covalent and hydrogen bonds are better described at the trimer level, and the FMO3-LCMO method is applicable to quantitative evaluations of a wide range of frontier orbitals in large biosystems. PMID:24028108

Kobori, Tomoki; Sodeyama, Keitaro; Otsuka, Takao; Tateyama, Yoshitaka; Tsuneyuki, Shinji

2013-09-01

429

Trimer effects in fragment molecular orbital-linear combination of molecular orbitals calculation of one-electron orbitals for biomolecules  

NASA Astrophysics Data System (ADS)

The fragment molecular orbital (FMO)-linear combination of molecular orbitals (LCMO) method incorporates as an efficient post-process calculation of one-electron orbitals of the whole system after the FMO total energy calculation. A straightforward way to increase the accuracy is inclusion of the trimer effect. Here, we derive a comprehensive formulation called the FMO3-LCMO method. To keep the computational costs of the trimer term low enough, we use a matrix-size reduction technique. We evaluated the accuracy and efficiency of the FMO3-LCMO scheme in model biological systems (alanine oligomer and chignolin). The results show that delocalized electronic orbitals with covalent and hydrogen bonds are better described at the trimer level, and the FMO3-LCMO method is applicable to quantitative evaluations of a wide range of frontier orbitals in large biosystems.

Kobori, Tomoki; Sodeyama, Keitaro; Otsuka, Takao; Tateyama, Yoshitaka; Tsuneyuki, Shinji

2013-09-01

430

Beagle 2 and NASA's Mars 2003 Orbiter: A Unique Exobiology Opportunity with an Orbiter  

Microsoft Academic Search

With the exploration strategy for Mars undergoing reexamination, the opportunity exists for the incorporation of the 60 kg Beagle 2 lander, developed in the United Kingdom for inclusion on ESA's 2003 Mars Express mission, with NASA's Mars 2003 orbiter derived from the Mars Global Orbiter. The combination of Beagle 2 with a Mars orbiter would result in a unique mission

Everett K. Gibson Jr.; Colin T. Pillinger; John Thatcher; Frances Westall

2000-01-01

431

Posttraumatic Orbital Emphysema: A Numerical Model  

PubMed Central

Orbital emphysema is a common symptom accompanying orbital fracture. The pathomechanism is still not recognized and the usually assumed cause, elevated pressure in the upper airways connected with sneezing or coughing, does not always contribute to the occurrence of this type of fracture. Observations based on the finite model (simulating blowout type fracture) of the deformations of the inferior orbital wall after a strike in its lower rim. Authors created a computer numeric model of the orbit with specified features—thickness and resilience modulus. During simulation an evenly spread 14400?N force was applied to the nodular points in the inferior rim (the maximal value not causing cracking of the outer rim, but only ruptures in the inferior wall). The observation was made from 1 · 10?3 to 1 · 10?2 second after a strike. Right after a strike dislocations of the inferior orbital wall toward the maxillary sinus were observed. Afterwards a retrograde wave of the dislocation of the inferior wall toward the orbit was noticed. Overall dislocation amplitude reached about 6?mm. Based on a numeric model of the orbit submitted to a strike in the inferior wall an existence of a retrograde shock wave causing orbital emphysema has been found. PMID:25309749

Skorek, Andrzej; Klosowski, Pawel; Plichta, Lukasz; Zmuda Trzebiatowski, Marcin; Lemski, Pawel

2014-01-01

432

FAST IR ORBIT FEEDBACK AT RHIC.  

SciTech Connect

Mechanical low-{beta} triplet vibrations lead to horizontal jitter of RHIC beams at frequencies around 10 Hz. The resulting beam offsets at the interaction points are considered detrimental to RHIC luminosity performance. To stabilize beam orbits at the interaction points, installation of a fast orbit feedback is foreseen. A prototype of this system is being developed and tested. Recent results will be presented.

MONTAG, C.; MICHNOFF, R.; SATOGATA, T.; ET AL.

2005-05-16

433

Aerobraking the Magellan spacecraft in Venus orbit  

Microsoft Academic Search

A spacecraft which was not designed for atmospheric entry was successfully flown in the sensible upper reaches of the atmosphere of Venus during the periapsis passes of more than 700 orbits, thus becoming the first spacecraft to demonstrate the use of aerobraklng to significantly alter the shape of its orbit at another planet.**The Atmosphere Explorer had successfully aerobraked In earth

David F. Doody

1995-01-01

434

Ultrasonically-aided percutaneous orbital aspiration.  

PubMed

Ultrasonography is the most effective diagnostic modality for locating and delimiting cystic orbital lesions, and may often provide an accurate tissue diagnosis. A case is presented demonstrating the ability of ultrasonography to aid in the percutaneous aspiration of selected orbital cystic lesions. PMID:523057

Skalka, H W; Callahan, M A

1979-11-01

435

Interagency Report on Orbital Debris, 1995  

NASA Technical Reports Server (NTRS)

This 1995 report updates the findings and recommendations of the 1989 report and reflects the authors' progress in understanding and managing the orbital debris environment. It provides an up-to-date portrait of their measurement, modeling, and mitigation efforts; and a set of recommendations outlining specific steps they should pursue, both domestically and internationally, to minimize the potential hazard posed by orbital debris.

1995-01-01

436

Electron Plasma Orbits from Competing Diocotron Drifts  

NASA Astrophysics Data System (ADS)

The perpendicular dynamics of a pure electron plasma column are investigated when the plasma spans two Penning-Malmberg traps with noncoinciding axes. The plasma executes noncircular orbits described by competing image-charge electric-field (diocotron) drifts from the two traps. A simple model is presented that predicts a set of nested orbits in agreement with observed plasma trajectories.

Hurst, N. C.; Danielson, J. R.; Baker, C. J.; Surko, C. M.

2014-07-01

437

Polynomial Bounds for Invariant Functions Separating Orbits  

E-print Network

Polynomial Bounds for Invariant Functions Separating Orbits Harlan Kadish University of Michigan July 3, 2010 Harlan Kadish 2010 CMS Summer Meeting #12;Outline Briefing on Separating Orbits A New Algorithm Complexity via Straight Line Programs How the Algorithm Works Harlan Kadish 2010 CMS Summer

Wehlau, David

438

Orbital fracture deterioration after scuba diving.  

PubMed

Sinus barotrauma is a common disease in divers. However, it is not familiar to maxillofacial surgeon. We presented orbital fracture deterioration by sinus barotrauma in scuba diving and a review of literatures. We also discussed the clinical features, the prevention, and the possible mechanism of orbital fracture deterioration after scuba diving. PMID:19625851

Nakatani, Hiroko; Yoshioka, Nobutaka

2009-07-01

439

A set modified equinoctial orbit elements  

Microsoft Academic Search

Modified equinoctial elements are introduced which are suitable for perturbation analysis of all kinds of orbit. Equations of motion in Lagrangian and Gaussian forms are derived. Identities connecting the partial derivatives of the disturbing function with respect to equinoctial elements are established. Numerical comparisons of the evolution of a perturbed, highly eccentric, elliptic orbit analysed in equinoctial elements and by

M. J. H. Walker; B. Ireland; Joyce Owens

1985-01-01

440

Spacecraft orbit determination using GPS navigation solutions  

Microsoft Academic Search

The orbit determination using the GPS navigation solutions for the KOMPSAT-1 spacecraft has been studied. The Cowell method of special perturbation theories was employed to develop a precision orbit propagation, and the perturbations due to geopotential, the gravity of the Sun and the Moon, solid Earth tides, ocean tides, the Earth's dynamic polar motion, solar radiation pressure, and atmospheric drag

Jae-Cheol Yoon; Byoung-Sun Lee; Kyu-Hong Choi

2000-01-01

441

Optimal orbits for Mars atmosphere remote sensing  

Microsoft Academic Search

Most of the spacecrafts currently around Mars (or planned to reach Mars in the near future) use Sun-synchronous or near-polar orbits. Such orbits offer a very poor sampling of the diurnal cycle. Yet, sampling the diurnal cycle is of key importance to study Mars meteorology and climate. A comprehensive remote sensing data set should have been obtained by the end

Michel Capderou; François Forget

2004-01-01

442

Guidance for an aeroassisted orbital transfer vehicle  

NASA Technical Reports Server (NTRS)

The use of atmospheric drag for slowing satellite in high energy, high apogee orbits to a lower energy, lower apogee orbit about the Earth is investigated. The high energy orbit is assumed to intercept the Earth's atmosphere. Guidance for the atmospheric phase of the trajectory may be done using the aerodynamic forces generated by the passage through the atmosphere. This research was concerned with the investigation of several methods of guidance during the atmospheric phase to cause a significant reduction in the final velocity as the vehicle leaves the atmosphere. In addition, the velocity direction was controlled to exit to a desired target orbit. Lastly excess aerodynamic lift was used to effect a plane change between the entry orbit plane and the exit orbit plane to achieve a desired orbit plane. The guidance methods were applied to a 3 degree-of-freedom simulation which included an oblate Earth gravity model and a rotating atmosphere. Simulation results were compared on the basis of speed of computation of the guidance parameters and amount of added velocity necessary to achieve the desired orbit.

Hall, Kenneth R.

1988-01-01

443

Orbit determination using synthetic aperture radar  

Microsoft Academic Search

The use of synthetic aperture radar (SAR) images to estimate orbital parameters is studied. The SAR image formation process which requires the ability to repeatedly transmit identical signals and accurately sense the return echoes from a region of terrain is described. The orbit determination capabilities of the SAR system's observables are investigated. Five SAR observations were collected from a simulated

W. L. Taber; S. P. Synnott; J. E. Riedel

1986-01-01

444

Orbital neurilemmoma: report of seven cases  

Microsoft Academic Search

Neurilemmoma (schwannoma) has a predilection for the head and neck, especially the eighth cranial nerve in the cerebellopontine angle. It rarely occurs in the orbit, representing only 1% of orbital tumours. We report seven cases. The nerve of origin was identifiable in four cases. Two occurred within the inferior oblique muscle. Five were treated successfully by anterior or lateral orbitotomy

Zahida A Butt; Alan A McNab

1998-01-01

445

Natural bond orbital analysis of steric interactions  

Microsoft Academic Search

We describe an ab initio procedure for extracting the Pauli exchange antisymmetry (“steric”) contributions to molecular potential energy in the framework of self-consistent-field molecular orbital (SCFMO) theory. This “natural steric analysis” method is based on natural bond orbital (NBO) representation of the SCFMO wave function, which allows the steric exchange energy to be approximated as an energy difference between “preorthogonal”

J. K. Badenhoop; F. Weinhold

1997-01-01

446

Moro: an european moon orbiting observatory  

NASA Astrophysics Data System (ADS)

We present the MORO Moon Orbiting Observatory during its phase A study. The context for ESA Intermediate mission M3 is described. We discuss general objectives for scientific lunar studies, specific reasons for a new orbiter around the Moon, and describe the science objectives of MORO and the MORO instruments and mission.

Foing, B. H.; Racca, G.

447

Preliminary ISAS Mercury orbiter mission design  

Microsoft Academic Search

This paper shows the recent results of ISAS Mercury orbiter mission study conducted by ISAS Mercury Exploration Working Group. Two options are under study; 1) A Spacecraft which utilizes Solar Electric Propulsion (SEP) as a primary propulsion system for interplanetary transfer phase as well as Mercury orbit insertion phase and 2) Conventional chemical propulsion spacecraft.

Hiroshi Yamakawa; Hirobumi Saito; Jun'ichiro Kawaguchi; Yasunori Kobayashi; Hajime Hayakawa; Toshinori Mukai

1999-01-01

448

Mars Climate Orbiter Mishap Investigation Board  

E-print Network

Mars Climate Orbiter Mishap Investigation Board Phase I Report November 10, 1999 #12;2 Table of Contents Mars Climate Orbiter Mishap Investigation Board Phase I Report Page Signature Page (Board Members) and Mars Polar Lander (MPL) Project Descriptions 9 2. MCO Mishap 13 3. Method of Investigation 15 4. MCO

Leveson, Nancy